The point is that you are not aware of what your choice will be...even when you really try to make an impartial random decision...secondly relevant data is relevant subjectively...furthermore the truly relevant data like avoid the speeding car is evidence of determinism n not the opposite.
Of course, relevance is subjective. We're talking about a SUBJECT making a decision.
I propose that we leave the issue of determinism aside. Your determinist tendencies are evidently esthetic and metaphysical in nature, you hate the idea of indeterminism. Yet hard-core material determinism only leads to complications and contradictions. Like if Harris is fully determined by his chemistry and other non-mental factors, then his philosophical reasoning is worthless. An argument can only mean something if you agree that reason has a role to play in this world, a causal dimension to it. Ideas matter, or they don't. They are not epiphenomena, or if they are, the very idea that they are is an epiphenomenon itself without consequence and validity, it's just neuronal noise. A scientist or philosopher who says: our ideas are predetermined by neuronal activity is basically saying: don't you take my babling too seriously, i'm just a machine saying nonsense.
In other words, any theory of the world, and of the mind, needs to account for its own emergence, for its own possibility as a valid, reason- and observation- based knowledge. Science presuposes the possibility of the human mind to be able to make sense of the world, so a scientific theory of the mind must make sense of sense itself. How can a chemical machine literaly make (produce) any real sense, in a hard-core materialist & determinist world view???
So let's agree that ideas matter, and have causality. You could of course argue that if ideas function in a causal way, they may still be predetermined by other ideas, so the world could still be determinist. That is true, and I am compatibilist in THAT SENSE and that sense only.
I just like you to properly explain at what point is the given choice "yours" only because you feel so ? When rationally calculated it is a necessary consequence when imaginarly not rational its is the product of unconscious processes which you cannot control, where is your alternative when alternatives are always an a posteriori judgement upon how you acted ?
I can have a theory of how minds work, like you say you have, that tries and take mental facts into consideration. There is no reason to assume that our conscient perception of ourselves is pure illusion, not anymore than seeing an apple fall from a tree is by necessity a pure illusion... There are however reasons to believe there's a large dose of recreated, virtual, buffered and selected information in what comes to our conscience. It's highly processed information, and it has is quirks and blind spots and errors and gliches, ok, but it FUNCTIONS, it plays a role, it paints an important image. We could not survive without our 5 senses, however weak they are, and we couldn't survive as minds without our capacity for mental introspection and observation. Mental facts are facts one need to account for.
All this to say that before I abandon the 'illusion of free will', I'd like to have some evidence it's indeed an illusion, for I have next to half a century of mental life behind me and remembers a good third of it perhaps, and that's a lot of mental facts pointing at free will to account for.