I had a duck egg that did almost exactly what you are describing with that one. I think I waited about 24 hours after he made the largish hole before I helped. Then I helped.
I would take him out, give him a little water with my finger (which he drank thirstily), moisten the membrane, then with tweezers I broke away some of the shell in the same pattern he would have done himself. Then I set him back in the bator. I repeated that several times over several hours, each time only breaking away a small amount. Eventually, he was able to break out of the shell himself, pushing it open just as if he'd zipped it himself.
Anyway, I suspect your little guy is stuck to the membrane from the humidity dip at the beginning, and can't turn to zip the shell. He will probably need help, and may be fine after that.
The duck I helped was just fine, although he died of unknown causes about a week later--I don't think it was related, but you never know. It is true that sometimes babies that have trouble hatching have a defect of some sort, and that may have later led to his death. But I am glad I helped him--at least he got a shot at life, and he had one very lovely week with us.
I am no expert, but if it were me, I'd give him a few more hours and then try the method I just described (and do a google search & a search on these forums, and you'll find lots of pictures and tips that will help--that's what I did too). Just be sure to go slowly, so you don't risk too much blood loss.