I think when the eggs got too dry that probably doomed them.
My question is why did you try to push the snake back in the egg?
I have had babies come halfway out only to go back in the egg and not come completely for several days.
Next time keep the egg box sealed up air tight until the last two weeks so it cant dry out and dont disturb hatchlings until they are completely out of the egg. They need to pip their head and start breathing for quite some time to increase their metabolism and absorb the rest of their yolk. I have seen this take several days before they decide to come out(always seems like the best snake in the clutch takes the longest).