What are my chances of getting into Stanford, USC, U Penn, or Brown University?

If you weren't prepared to sit the exam again, why didn't you cancel your scores while you still had the chance? Then Stanford would never have seen them. It is an option to take the ACT instead so you never have to send any of your SAT scores, though. Unfortunately, your grades are higher than your SAT II scores, which suggests to the admissions officers that your teachers are easy graders or that grade inflation is rampant at your school, devaluing your good grades. Try the ACT. Hope that helps.