Chances of success (2 questions)

I am currently a Junior, and have a 4.0 weighted GPA, along with a 69 in Honors physics. (yay) I go to one of the top 20 schools in the country, I do “well” in all my classes. I’m in debate, in Psychology club, chess club, and am in the 94th percentile in English on the PSAT. I get A’s in pretty much all my honors classes, and high-mid tier B’s in my AP’s. However i’m really worried how my outcome in physics after this first semester will impact my college admission. Assuming I get my final grade in the class to average out to something like a 77, how badly will this hurt me long term. Secondly, when I took the PSAT sophomore year I did ok. I took it again this year and got the same score, except my English score rose a lot, and my math dropped a lot. I am also currently challenged significantly in my honors Algebra 2 class. I still have a B, but I used to be so good at math. But now I stink. How can I change this?
Thanks