As the tmux interface is shown as part of the terminal's contents, there is no way for it to bypass the usual constraints of a terminal display – it's always going to be a strict grid with exactly the same character width and height in every line, whether it happens to be the tmux status line or something else. In short, the bar will always be one-line-tall and that's that.
Your best option is to make it less distracting by tweaking the colors and layout, e.g. dimming down the orange highlight or removing the one-space padding around the number, or even setting the background to "none" to make it transparent (which I'm not sure if tmux can do, but it ought to be able to).
Since you apparently have a very custom config installed, you'll need to find where that's done, but ordinarily it would be window-status-current-format
and/or window-status-current-style
in the tmux config.