to get better than a 1990 SAT on the ACT, you should aim for 30+ (source: http://blog.prepscholar.com/act-to-sat-conversion)
also, i am in ap stats and to be honest, it really helps very little on ACT science.
having a broad (and accurate) knowledge of the 3 main science subjects (bio, chem, physics) is really helpful.
even more helpful is being able to read graphs and data tables (so if ap stats taught u that, then i guess it would be very helpful)
your sat writing and reading scores probably indicate you will get around 32 subscore, which is good if u want 30+