Sticking to OP’s actual ask (chances at the schools he’s listed)…
MIT: I think you have a much better than average chance due to your USAMO and AMC. Perhaps @hebegebe can weigh in.
Very good chance at UIUC EA, UVA and USC in my opinion. GT can be iffy sometimes for OOS but you’re a solid candidate.
Now the question is, can you actually afford to attend if admitted? You haven’t mentioned an actual budget and what your NPC was at these schools.