I'll chime in - trying to move today, so this will be quick:
The slime layer you see is normal. It's fine to wipe it off.
The pup might not move in the egg for extended periods.
Make sure the yolk and chord haven't rolled around. It pinches the chord and breaks the connection to the pup. If that happens, the pup won't usually make it.
I wouldn't suggest freeing a shark from the egg. I've done it before, but only on rare cases. 999 times out of 10,000 the shark will use the entire yolk sac, then hatch a few days later. As they get close to the hatch date, the pup will drawn in more from the yolk that it needs, and store it. That is why you don't feed shark/ray pups right away, they need to burn off the extra stored nutrients. Also, helping one out breaks part of the growth process - pushing free of the egg. Similar with birds and reptiles - helping them out of the egg actually sets them back.
An upclose picture would help. But that's my $.02 on it. Keep us posted.