What is the latest you can take SAT IIs in time for ED/RD? How does the ACT replace them?

I’m assuming October and December respectively? Asking because I’m not happy with my Math II scores. I’ll be taking the SAT again in October which puts me in a pickle subject test wise. I doubt November scores will count for ED but I have to ask, will they?

I will be taking the ACT with Writing in September. How exactly does this “replace” SAT subject tests?