I have not made an appeal to any probabilistic scientific claim , rather i have made an appeal to the established scientific facts for which there can be no alternate description. QM does not falsify anything that i have said as you are yet to show a clear link between free will and QM. Keep it in mind that the non-locality in QM can show some ultimate fixation negating free will at all. If you mentioned QM to show that reality may have alternate description or it may have randomness then that does not work. There is no unanimity between the physicists about the status of randomness and probabilistic description of reality in QM that it is something ultimate or this disorder have an order deep down. A better option in the favor of alternate description of reality would have been to click the concept of possible worlds in modal logic. That would have made sense. Your second objection does not work as well. It might be true that due to determinism i might not be able established the fact of the statement in which i deny free will but that does not mean that i have not established the truth. It is the genetic fallacy , trying to falsify a statement by explaining away its origins.