>and given that QM effects don't scale to molecular level, that leaves only determinism

This is simply wrong. Quantum effects affect your choices more than it might seem possible. The wrong atom decays in the wrong place in your body mutating your DNA, that one too much string of DNA that starts a tumor, which means chemotherapy. That does seem to affect your choices.

Or instead of Shroedinger's cat you use it to trigger something, buy or sell some stock. Which clearly affects your future, one way or another.

I never really understood why humans keep insisting stochastic processes do not affect their choices and their future. It's very short sighted.

Hell, even brownian noise in your brain can affect your ideas, that one random spark out of nowhere, that one neuron that's pushed over the triggering edge. There's so much stuff all around us affecting us constantly. One neutrino interacting a the wrong time (average one does interact with our bodies across whole life, I remember reading), one cosmic ray.