Maybe just do the occasional Math practice test to keep your testing skills sharp. Even with a superscore the schools will likely see all your scores in the mix. If your math score dips a bit it’s no problem but better too keep it to a level that doesn’t raise eyebrows.
For ERW, I recommend Erica Meltzer’s books…she has guides for both the SAT and ACT. She actually helped design past tests so she knows her stuff.