If you believe in an all-powerful God, then God already knows everything you will do, and knew it from the instant of creation, basically guaranteeing that you cannot do other than you have done. God’s foreknowledge seems to preclude any hope of free will.

You're conflating freedom with foreknowledge. Me knowing my roommate is going to visit her girlfriend tomorrow because I heard him on the phone does not in any shape interfere with his freedom. Same thing with God who can read your mind and see your heart. The existence of contra-causal freewill which is necessary for not only responsibility but also rationality is the ultimate proof for the existence of a trustworthy Creator. If you're interested in the topic, check my video out: