ACT or SAT?

I’ve been studying for ACT all summer and my scores were basically the same throughout. Not a good score, without superscoring they’re all 31. The one I took in junior year as a practice run was a 28. (yikes!)
I signed up for the September ACT, and yesterday I thought that maybe I should take the SAT not the ACT. I took a practice test today and I got a 1410 (680 R/W, 730M). I’ve been doing better in Math and English/Writing on the ACT than this SAT PT, but my Reading scores were really bad and I screwed up science everytime biology passages were on (I never took the course).
Should I take the October SAT? I took SAT subject tests on August, I think they went OK enough to not have to retake them but I’m no way 100% sure about that (and scores don’t come out until after late fee applies). Another problem is that I may apply EA. Then I only have 2 SAT dates left, and if I have to retake subject tests, only 1 for the reasoning.