A big part of the issue: “Amherst, Bates, BC, BU, Bowdoin, Clark, Holycross, Georgetown, Johns Hopkins, Northeastern, Northwestern, Penn State, Princeton, Rutgers, Syracuse, Tufts, UChicago, Upenn, and Villanova.” Rutgers, Villanova, maybe HC are easier than the others.
Then, the fact it’s a stem course and you want a stem path.
For the tippy tops and tops, the competition is fierce and many kids will have both the scores and only A grades.
If you’re firm about aiming high, you need to resolve this. Or will have trouble progressing in math, in hs and in college. You need to understand what it is about the tests vs homework that’s slaying you. What feedback have you gotten from the teacher after tests? Ever ask peers for study help?
How truly important is the academic conference vs college options? What is it?
For the record, a summer teacher might not explain better, have convenient times to chat, or grade easier. Online is not necessarily a bad idea. But in either case, you’d need a strong grade, dedication to every effort it needs.