Thread the bolt back in to where it bottoms out then back it off 1/8". Protect it with a piece of leather or tough plastic and give it a good shot with a hammer. Don't try to tap it out, that just beats up the bolt, hit it like you're driving a 10 penny nail. You'll know it's free because the bolt will drop.

Now if with the wedge free you should be able twist the stem and work it up. If it's still tight or frozen to the steerer don't hold the wheel between your knees and force it. That often twists the fork. Instead, remove the wheel and drop the fork over a 2x4 clamped in a vise so the blades are held up near the crown and can't bend or twist.