It remains too difficult to chance you. You are certainly not worse than the average legacy, so best guess 15-20%? Have a lot of backup plans. Outside classes are fine, but they do not move the needle much. Colleges including Duke only expect you to take the most challenging courses within the school: as long as you did not avoid a hard AP in the school to instead take it outside the school you are fine. No colleges like the practice of taking an offered AP outside the high school unless there are compelling circumstances. Your rank top5% is excellent —that is surprising with your unweighted GPA but as those on here know it is vastly different among high schools, and relative grades within high school matters more than the actual number. In any case, you are great there.
My D is a humanities kid who had erbw SAT around the 75th%ile CDS and a math SAT within the middle 50%, 3.9 uw, every top course taken, all As junior yr with max rigor, the couple of Bs early in HS were in stem(one was a B+ AP chem in 10th gr which is notoriously difficult and only a few attempt it in 10th). ECs were excellent including concertmaster, some regional awards, extensive EC with leadership every summer, girl scout gold award (akin to eagle scout) , faculty academic awards from school and excellent essays, LOR. One teacher LOR said best student in a certain area in over a decade. Her gpa/rank was the relative weakness but was within the range unhooked kids had gotten in based on naviance for the school. Her hook was legacy nothing else. ED is your best bet though certainly could try RD: they do take legacies. Our other D did not do any EDs and got in Duke RD as a legacy as well as multiple other top-10s unhooked , however she was an outlier at her school, almost all A+ with the highest rigor of anyone, valedictorian, all 5s , almost perfect scores, many top academic and EC recognitions at the state /regional level and also top LORs. Good luck! You definitely have a shot!