First off all, I hope and pray you recover quickly!
Secondly, I want to preface my answer by letting you know that while I have been a life-long Christian, my answers are going to probably be a bit different than the others here. Whilst raised with standard protestant perspectives, I became very interested in theology in high school when my dad started his ordination process - and it has become a life long passion. As a result of my studies, my views have changed drastically. For instance: I am no longer a Trinitarian, which will become relevant to some of your questions. However, while my interpretations are not main stream, drawing doctrine through the proper interpretation of scripture is still fundamental to my approach to theology; and informed by external sources that provide historical context and details that are missing from the scriptures. I'm not a fundamentalist who thinks scripture has no errors in it, nor am I a so-called "liberal theologian" who attempts to dismiss God, miracles, etc. from my interpretations - I always seek to first and foremost understand what the intended teachings of the scriptures are.
I struggle with accepting Jesus as the messiah given Jewish
prophecy/law. So for example:
Isaiah 53 speaks of the Messiah coming as a suffering servant, One who
is led as a lamb to the slaughter and who takes our sorrows,
infirmities, and punishment on Himself.
In this particular case for example no one can fulfill my obligations
under Jewish law; facetious as it may sound no one can honor the
commandments on my behalf or eat kosher on my behalf these are my
obligations so I do not understand the Christian belief that through
Jesus I am saved. He cannot my sins and my responsibilities for
atonement onto himself per Jewish law.
Jesus himself said that he did not come to abolish the Law or the Prophets - but to fulfill them. Furthermore, he taught that the one who keeps the Law and teaches others to do the same will be great in the kingdom - while one who teaches others to not follow the Law will be least in the kingdom. In fact, he said that in order to even get into the kingdom your righteousness must surpass that of the Pharisees (Matthew 5:17-20).
Contrary to what many say - Jesus and the rest of the NT do not teach that nothing is required of you. Even though Gentiles aren't required to convert to Judaism and enter into the Mosaic Covenant - we yet have God's Law. That is, after all, the promise of the New Covenant: that God would write his Law on our hearts and we would be His people.
Furthermore, Christ actually taught us to go above and beyond the Mosaic Law. The Mosaic Law, after all, is not the perfect will of God - but a compromise between God and sinful man. Hence the Mosaic Law permits divorce. It specifies all kinds of sacrifices for sins - even though God's will is that you don't sin in the first place. Hence in Isaiah God laments all of the sacrifices and festivals - even though they are in the Law given through Moses. The Mosaic Law permits slavery - even though when God created man and woman they were equal. It was only in the fall that women were made subservient to men; the beginning of inequality and slavery. The ideal - as found in Christ - is that there is no Jew nor Gentile, male nor female, slave nor freeman; but that we all be united as one people (Galatians 3:28).
After all, the Law specifies what is required of us. What reward is there for not murdering and not stealing or the like? These are simply basic moral stipulations that are required of all of us. So the Law only condemns us as sinners - it does not make one righteous. Nevertheless, the Law points us towards God - for God is love. If someone wrongs you - forgive them. If they slap you - present your other cheek. If they want to steal your cloak, give them your shirt as well, etc. These aren't moral precepts that Christ taught - he is instructing us to go beyond what morality, what the Law requires of us and to sacrifice of ourselves for the sake of God and our fellowman.
So yes - as a Jew under the Mosaic Law, you should keep the Law to the best of your ability. But if you would follow Christ's teachings, then you must move beyond the requirements of the Law and give all of yourself to God, sacrificing everything. For by losing your life you will save it.
Now you may ask, why did Christ then die if we are still required to follow God's Law? Just as the Nohaide and Mosaic Covenants were ratified by blood - so too was the New Covenant ratified by the blood of Christ. For the blood is life; and Christ lived a life in perfect obedience to God's Will - even to his death. And the New Covenant was necessary because the Mosaic Covenant was made with the flesh - to the physical descendants of Israel. But righteousness cannot be inherited by the flesh. Try as you might, each generation and each individual must struggle with good and evil, and with whether they will live for God or for their sinful desires. And so over and over again the Covenant has been broken by Israel overtime - and they have suffered the consequences accordingly.
The New Covenant is not made with the flesh - but with those who live in the Spirit; those who know and walk according to God's Law proper; those who live by love. Christ said that those who do the will of God are his mother, and brothers, and sisters (Matthew 12:50).
And we observe this design all the way back in Genesis with Cain, Abel, and Seth. For Abel was righteous - for he did what was right. Cain slays Abel and is banished from the Lord's presence, is cursed so that the earth will no longer give up its strength to him, and is cursed to wander. Eve subsequently gave birth to Seth, and she says that God gave her Seth in place of Abel. And through Seth we get a righteous line of people (vs the violent line of Cain).
This design pops up again with the final three plagues: locusts, darkness, and the death of the firstborn. First the locusts represents Cain's curse of the earth no longer giving up its strength to him - via the locusts eating all the vegetation. Next the light over Israel represents God's favor and presence with Israel, whereas the darkness represents Cain's being cast out of God's presence. Finally, in the last plague the slain lamb/goat represents Abel - the blood of the righteous causing judgement to passover - whilst Israel = Seth, the righteous line given in his place - descendants of Abel in accordance by their deeds rather than by their genes.
Again, we have Yom Kippur with the two goats - one chosen for the Lord and the other as the scapegoat. The one chosen for the Lord is as Abel, and is slain for the sins of Israel. The scapegoat - like Cain - is banished from the Lord's presence and is cursed to wander in the wilderness. Israel is in turn symbolically Seth - the righteous line that is given in place of Abel.
So you see, Christ dying for our sins is perfectly in line with the model of salvation established by God in the Hebrew Bible. Christ is Abel, Christ is the passover lamb, Christ is the goat of the Lord on Yom Kippur, etc. And during his own trial - Barabbas served as Cain, and the scapegoat.
Second, the Talmud as well as historical documents recognize two
messiahs: one messiah being the son of Joseph and two Davidic
messiahs. From my reading of the historic documents Jesus clearly
meets the criteria of the messiah son of Joseph while does not
necessarily meet by Jewish standards the criteria of the Davidic
messiah. Why can we not accept Jesus as the messiah ben joseph?
Moses prophesied that God would raise up one like himself from among the people. Moses was a priest (even higher than Aaron the High Priest), a ruler of Israel, a prophet, and a savior of Israel. However, through sin these roles became divided so that under the Mosaic Covenant only particular lines could hold particular offices.
A priest had to be a descendant of Aaron in the Mosaic Covenant. But Aaron got raises to his position as Moses’ prophet because Moses sinned annd would not do as the Lord said, but insisted that he send someone else.
Again, Israel was supposed to be a nation of priests for all firstborns were to be dedicated to God. However, after the Golden Calf incident God changed his mind and took the Levites instead of the firstborns of all the tribes.
For a time Israel was ruled by prophets and judges - but then they sinfully demanded to have a King like other nations. So they got Saul who was replaced by David. But David wasn't descended from Aaron, so it is impossible that under the Mosaic Covenant that there could be one person to hold the office of both King and Priest.
This is undoubtedly why there are multiple such Messiah figures in the Rabbinic tradition; because it would be impossible under the Mosaic Covenant for these roles to be united under one figure. However, the Messiah is someone who will restore all things. This means that the true Messiah - as the one like Moses - must also fulfill all these offices. And the only way that that can happen is through the establishment of the New Covenant and the establishment of a corresponding new priesthood. For in Christianity, all are priests - all are called to serve God. And there is no physical Christian nation - but the kingdom is manifested anywhere and everywhere that we do the will of God.
Third, I don't understand how the current Christian practice doesn't
violate the Jewish prohibition against idolatry or the 1st
commandment.
As I noted earlier, I am not a Trinitarian myself - though I was raised such. Rather, I argue that we should follow the biblical precedent in the Hebrew Bible where Moses is said to be God (Exodus 7:1), angels are are addressed as if God and speak as if God (like the angel in the burning bush in Exodus 3), and Jesus interprets the Psalms as saying that those who have received the Word of God are "gods" (John 10:34-35). None of these are treated as false gods - like those worshiped by other nations - but rather are addressed as God due to their being God's representatives. Since Christ is the perfect representative of God - always acting precisely as God has instructed and wills - and as the one like Moses, it is natural then that Jesus also be addressed as God in the same sense as Moses.
Unfortunately, after 70 AD and the start of the Jewish Diaspora the gentiles were left to interpret scripture without a strong Jewish-Christian voice like Paul. The Church Fathers who were educated so as to write theological treatises and leave their impact on the formation of Church doctrine were ones who had recieved education in Greek Philosophy and such - and they tended to have great adoration for Plato. This was bolstered by tales of how Plato had gotten his ideas from Moses. In Alexandria they also had the Helenistic interpretations of Philo Judeaus; whom St. Jerome considered to be a "genius."
Finally, the worst thing possible happened and Constantine made Christianity the state religion. Not only was this contrary previous teachings (The kingdom is of heaven, not a worldly nation) but out of fear of schism Constantine initiated the Nicean Council to try to get the Church to standardize its beliefs. This led to beuracracy and ever shifting politics deciding what doctrines Christians had to agree to - lest "in the name of God" other "Christians" do horrible things to them like banishment and death.
The establishment of "orthodoxy" is, IMO, fundamentally erroneous and the source of many of the evils done in God's name. Nothing wrong with tradition mind - there is great value in tradition. But when tradition becomes blindly enforced and deviance is treated as heresy - you are no longer allowing God to work in people, nor for individual's to grow spiritually. Questioning becomes the same as putting your salvation in jeopardy - which is why so many Christians today are afraid of honestly studying and engaging with competing view points... I could keep going on this topic - but I don't want to deviate too much from your main questions :)
Fourth, is it not sufficient for me to consider Jesus a rabbi?
Unpopular opinion (again): While salvation is through Christ, I am not of the mind that one's doctrines determine whether one is saved or not. As talked about brilliantly in James 2, faith devoid of action is dead and cannot save you. The value of belief is that it serves to guide your actions - but it is your actions that you are judged by.
In Romans 2, Paul talks about how Gentiles - despite not having received the Mosaic Law - have yet become a Law unto themselves; their conscience both serving to defend and condemn them before God. It is those who pursue what is right and good with their life that are rewarded eternal life.
To defend this notion, let us consider the model of salvation in the Hebrew Bible once more. Who was saved in the flood? Noah himself - the righteous prophet - and those near and dear to him: his wife, sons, and his son's wives. And of course all the animals.
And in the 10th plague, who did Moses save? Ie: who did he instruct about the passover? For the plague didn't specifically passover the Hebrews, but anyone household with the blood of the lamb/goat on the doorposts and lintel. This knowledge Moses only shared with His people; his fellow Jews that he sought to save from slavery. And those who obeyed (which, uncharacteristically, was all of them this time) were saved.
So we see that those who are known by the righteous prophet in question are saved. Likewise, in several places in the NT in talking about the judgement, Jesus says that it is not sufficient to cry "Lord, Lord" to be saved - he will reject you before the Father saying "I never knew you."
The question then becomes: how is it that we can be known by Jesus and, in turn, by God? Here is what I have found: the one through whom the love of God is made known shall in turn be made known to God through those that have been shown love.
For instance, in the parable of the sheep and goats where Jesus is judging between those who will be rewarded with eternal life and those to be punished, the criteria has nothing to do with doctrine. Instead, they are differentiated based upon their actions towards the least of these. And he takes it a step further says that whatever you have done for the least of these you have done for Him, and whatever you did not do for the least of these you did not do for Him (Matthew 25:31-46).
And I would like to offer one last thought for you to consider: It is not possible for another Messiah to come after Jesus anymore than it was possible for the magicians in Egypt to once more turn the Nile to blood. After all, in order to demonstrate that they could truly do the same thing as the LORD, they would first have to turn the Nile back into water. But if they could do that - then Pharaoh would not have needed to ask Moses to call off the plague.
Similarly, the nations already worship the God of Abraham, Isaac and Jacob. False prophets may come and claim to be the Messiah - but they are powerless against the blood of Christ; at best they can hope to mimic him on small scale. Like how the magicians might have used the ground water - left unpolluted by the Lord - to try to replicate the Nile turning to blood. The only one who could turn the nations away from God now would be by an act of God - but why would God drive people away from worshiping Him? So then, there can be no other Messiah but Jesus.
I hope this helps :)