AP classes

Personally, I understand what you mean by being scared of possibly spreading yourself too thin. For this reason, and the fact that you have gotten B's that have hurt your GPA while applying to Ivy schools, I would recommend to not add on another AP class. While academic rigor is important for these schools and APs taken are considered, I would believe that staying where you are and possibly focusing on keeping the grades up instead of risking the grades to slip is the best option. Having 9 ECs seems like you are already very busy too, and so I would be worried that it would just become too much. Lastly, its your senior year! We all deserve to have some time to ourselves and be kids while we are! I heavily valued self care this year and it came back tenfold in terms of my positive grades, so maybe giving yourself time can actually give you even better grades than the years before! Of course, I do not know everything going on academically and this, at the end of the day, is just me, a stranger, giving you some advice based on a paragraph of information. At the end of the day, I think you've got this and it appears to me you clearly have ambition and are willing to work towards your goals <3