Superdeterminism just says that there is no statical independence. Not sure where you are getting the future determines the past from that. However, yes, in a deterministic world there is only one way to get to a certain future, so I guess the future does indeed determine the past. Is that what you mean?

No, I mean that classical determinism says "here is the current set of particle positions/momentums/etc, so we can work forward and predict everything from that." Superdeterminism says "if you do X then you will learn Y, so you aren't going to do X."

That doesn't necessarily mean signals going back in time. It could mean that the initial condition of the universe was set, such that nobody would do X. But that's still a way of the past (initial condition) being determined by the future, even if the future was just predicted via determinism. It makes physics teleological.

A common criticism of superdeterminism is that it eliminates falsifiability from science. E.g. to quote physicist Nicolas Gisin, "If we did not have free will, we could never decide to test a scientific theory. We could live in a world where objects tend to fly up in the air but be programmed to look only when they are in the process of falling." https://en.wikiquote.org/wiki/Superdeterminism

The rebuttal from someone more knowledgeable in the field than I am: https://youtu.be/YglT09Korr0?t=1115

So her criticism #3 of essentially my second paragraph is that you can't assume anything, because we don't actually have a superdeterministic theory to evaluate. Maybe there's a dynamic law we haven't figured out that could make it work without initial fine tuning.

Fair enough I guess, but I'm not convinced it's a good answer to say "I think a theory with property X is the answer, and you can't criticize it because I have no actual theory with property X." I think it makes more sense to give little credence to superdeterminism until someone comes up with a plausible superdeterministic theory.