Any Nihilists here?

[Bucky Ball]

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.  So free will remains a matter of faith.

There is no doubt that whatever decision is made "in the moment", is 100 % dependent on what "is already" 
in the electrical circuitry (? "memory" ) of the human brain. If not, please play for me the Emperor Concerto, right now.
One of my favorite researchers : https://eagleman.com/