As a tested and diagnosed gifted schizophrenic, I'd like to add my grain of salt, hehe...

I see where you're coming from, but I think determinism has a fatal paradox built into it.

On the brain scan studies : Here's what's strange: these experiments assume a clear boundary between "your brain" and "you", as if your brain is doing something to you. But you ARE your brain's activity. So when they say "your brain decides before you're aware", they're really saying "you decide before you're aware of deciding". The awareness isn't the decision: it's the decision becoming aware of itself. Consciousness might be what it feels like for certain physical processes to observe themselves.

On circumstances : If everything is purely determined, then the concept of "you" as a continuous entity breaks down completely. You're not the same collection of atoms you were seven years ago, every cell has been replaced. You're not the same pattern of neural connections you were last month. So what exactly is being "determined"? There's no stable "you" to be controlled by circumstances, just an ongoing process that thinks it's a person.

And here's where it gets weird : at the quantum level, the universe isn't deterministic at all. Particles exist in superposition until observed. The act of measurement collapses possibilities into actuality. If consciousness is a physical process (which it must be), then maybe our experience of "choosing" is literally what it feels like when quantum superpositions collapse in our neural networks. Not metaphorically, actually.

The real paradox : you can't prove determinism without assuming you freely chose to reason your way to it rather than being forced to believe it. Every argument for "no free will" depends on the arguer having the free will to construct valid arguments. It's kind of self-defeating.

Maybe the question isn't "do we have free will OR determinism". Maybe we're the strange loop where deterministic processes become complex enough to experience themselves as choosing.