Every argument against determinism comes from the perspective that the conclusions of the argument are intolerable. This is not a slight to you. This is the argument put forth by people like Daniel Dennett. I think the field is primed for someone who can back up the argument using the physical sciences, but so far there’s not a lot there.

Let’s do a thought experiment that I call the Reverse Ship of Theseus. The Ship of Theseus is a philosophical demonstration of the origin of identity - if Theseus’ ship were to have, in the course of his voyages, every board, mast, sail, and nail replaced - one by one - does he return in the same ship he left with? In the Reverse version, we replace every neuron in your head (and if you take a more holistic view, every cell in your body) with one from Charles Manson. Every state of every neuron and all of those interconnections are replicated. All of the hormones, neurotransmitters, excitatory and inhibitory chemical reactions are perfectly replicated. Every bit of Manson’s history, from before he was born or even conceived, through his childhood and adulthood, is deterministically encoded in your cells.

At what point do you become Charles Manson? Christian philosopher CS Lewis famously wrote

“You do not have a soul. You are a soul. You have a body.”

In a materialist worldview, of course, that’s nonsense. The thing to which I’m referring when I say “me” is an emergent phenomenon of a host of physical properties and dynamics on a scale that is, still today, incomprehensible. There’s no “self.” The self is a convenient psychological illusion that allows me to say “This is my hand,” or “That self over there, approaching me with a machete, is a danger to my self.” Even here, we’re not talking a radical point of view. This is where a lot of Buddhist schools have come to similar conclusions, for instance.

I am not a murderer. Is it because I choose not to murder, or is it because I did not receive a traumatic brain injury on top of having an abusive childhood in a violent environment where murder was something I encountered regularly, and would even be considered a rite of passage and garner social approval?

I can think that I choose not to murder because I am compassionate and empathic. But those attributes, were you to swap my brain for Manson’s, would turn Manson into a largely well-behaved pro-social academic with an aptitude for mathematics and a desire to create safe spaces for people.

I do agree with you, though, that you cannot rescue the free will concept by retreating into areas like complexity theory (which I do know a bit about) or quantum theory and physical indeterminacy (which is not my field).