Ya, those numbers are good enough. Don't know about top 20s though. Try lawschoolpredictor. I tried it with and without checking the box for URM: the difference is amazing. It can change the whole screen from reds to greens. I'm not sure how accurate it is, I've found at least two errors myself.
There is an organization, the Law School Project (I think that's the name), that claims to help Native Americans get into law school, but they ask for money so be leery. Good luck.