Any Nihilists here?

[GrandizerII]

You don't need to go through all that trouble to have "epistemic access" to counterfactuals. Counterfactuals are right there, in your mind. Unless, of course, you're talking about concrete possible worlds here, and not just abstact?

Also, there are different flavors of "free will".

Alice and Bob measure a stream a particle-pairs in a singlet state.  Alice sets her polarizer at 37.5 degrees off vertical, and Bob sets his to 77.4 degrees off vertical.  We believe Bob could have set his detector to any orientation but all we know is that he set it to that one.

That's fair. I would agree that believing Bob could have set his detector to some other orientation is a different sort of doxastic attitude than knowing that he set it to one specific setting.

And it seems like you were referring to concrete counterfactuals anyway in your case against "free will".