If hatch time is close I'd leave be. If more than a couple days away I would carefully seal the crack with the nail polish. My wife uses super glue to mend cuts and repair teeth on herself and me. I wonder how that would work with egg cracks/holes.
NOW I see the pictures! I'd try a repair job, but the cracks look all the way through the membrane. I'd worry that the polish would get inside the egg. I believe I would use wax. Those cracks look bad; good chance the embryo has already been compromised and will die as a result. Even so, I'd try... Good luck
Possibly. With something like this it is a matter of wait and see. I have doubts they will make it to hatching, but...who knows. Just when you think the egg is ruined it hatches.