Disagree as I know several students with similar stats at Ivy League schools (especially Princeton). However, there are very few and some of the prep schools did not assign class rank, but I can assure you that several were not among the top half of their respective class.
Each student attended private prep schools with most attending super-elite boarding schools for high school.
OP: Please read my post as I can assure you that none of the other students had a R&W SAT score as high as your score. The SAT math score is easily addressed (based on your math courses & grades in those courses), plus you are retaking the SAT.
Your SAT score is not just a 1300, it is a 790 R&W combined with a Math score that does not accurately reflect your Math ability based on your math courses taken in high school.
Agree that you need to focus on schools which offer full needs financial aid (tuition, fees, room & board, possibly books & health insurance).
Also, if needed, you can request an application fee waiver from the schools which I listed.
Agree that QuestBridge is a program that you should consider.
Repeating the list of schools that I suggested in my earlier post:
Princeton, Yale, Amherst College, Grinnell College, Smith College, & Wellesley College.
Also, since your brother is at a super-elite university (WashUStL), you may have some insight as to the work demands expected & required at these type of universities.