don't know if you're still searching, but I found a really nice solution to this problem (and it's not changing your OS to linux :D) it's called tastiera italiana aggiornata. It offers you a new complete layout for the IT keyboard layout, giving you an easy access to a bunch of characters that are not originally in the italian keyboard, such as ˜
or the reverse tick. Here's the link of the website, it's a driver that you install replacing the original windows driver. It's all explained in their website.