Thank you for your kind comments and very interesting argument. Yes, freedom is a relation, whether it is freedom from or freedom to. So our free will would be a relation to the world, whether conceived as a whole or to any part in it. But I think the notion of a causal chain is the red herring in the discussion of free will, even though I grant that sounds counter-intuitive. Determinism is, as you say, when a cause necessarily results in one outcome. Denial of free will is the a priori assumption that a causal chain of necessity is the cause of all events (and I like how you define and use “event.”) That a priori assumption leaves no room for there to be any meaningful free will because the assumption assumes its conclusion — a circular argument.
To me the question is whether we have choice. And though I am not sure I understand or agree with your concept of “the place human consciousness occupies on the spectrum of freedom,” I would say that human choice is part of the causal “mix” that is a field or spectrum, not a chain. The idea of a causal chain is to place a false model on reality. In the sense of a field of causation of events, human choice is in that field. So human freedom is a loose and stellate relation with the field of other entities in the world. One could also say that human consciousness bends the universe in a similar but different way that mass bends physical spacetime, though a quantam analogy is probably more appropriate.
Your portrayal of the idea of free will as a ”shared fiction” is quite ingenious. I definitely like the concept of useful fictions, ala Nietzsche, but I wouldn’t include free will in that category. Free will is empirically verifiable, deniable only be an a priori decision to preclude its reality. Could society function while denying the reality of free will? Probably. But it would be a very different society; one in which human actions are of no more significance than the way the wind blows. But with respect, I think you missed the point of my argument against the denial of free will and how it is used as a means of political domination. People have free will, but part of having that freedom means that people can voluntarily give it up, and that’s where manipulation, like telling people they have no free will, can fool people into being dominated.