I really appreciate how you have described things here, and I hope that this helps the opening poster understand.
I'll add a few musings to the pot.
Human ignorance of the future is limited human perception of possibility. I can allow that I don't know what will happen, and as such multiple things can be possible, from my very limited perspective, because of my ignorance. But this is not true for God, Who knows the end from the beginning; and Who works all things according to the counsel of His will (Eph. 1:11). My limited, inadequate perception of the future is catastrophically less determinative than God's unlimited, perfect knowledge of all things, past, present, and future. So I can grant the appearance of certain things from a limited, ignorant human perspective that are impossible to be otherwise, from God's perspective.
Ultimate ontological possibility places chance in the driver's seat. Chance is one of those annoying features of libertarian freedom for its advocates, and it will remain as long as they assert the ability to do otherwise. For the only way one can do otherwise, is if he/she actually can "be" otherwise than what he is at the moment of choice. It's that "chance" component that mows down the coherence of the very idea of responsibility for libertarian freedom. But every time that libertarian advocates try to argue against chance; they also argue against their own principle, the ability to do otherwise (sometimes called the principle of alternate possibilities: pap for short).
Big distinction being made between "perceptual possibility" and "ontological possibility".
