Depending on what you’re planning on going into, don’t lock yourself into going to university. My wife spent 3 years of half course load at university while working in the same field she was trying to study in and didn’t get her degree, or actually get into the faculty she needed for that degree. She is now 5 months from her degree after spending a year and a half at college in a workplace program. Academia is disgustingly bloated and “you have to prove you want to be here before you can go into what you actually want to learn” for certain disciplines. College is a perfectly good, or better option depending on what you are going into.

I would refer to that as thickness, but I’m not a jeweller. My advice stays the same though, try some on and see what you like.

My wedding band is ~8 mm and i’ve never worn a ring less than 4 at its narrowest point. I would say just find something you like the look of, and see if you can find something at a jeweller that’s similar you can try on if you’re that worried about the fit.