(I merged all the threads into one so the info isn't all spread out for you.)
Right now, the best thing you can do is wait. You can't really do anything to help it hatch at this point. The air is out, so that's good. If you can't see a yolk sac, chances are it's not a good egg. Sometimes it's hard to see on the smaller sharks. Give it a bit and see what happens. If it's a good egg, in time it will hatch. At that point your next challenge will be getting it to eat. Don't try to feed it right away, give it a day or so to allow it to use up the extra energy it absorbed from the yolk sac right before hatching. Ocean Nutrion makes a shark/ray frozen food that works great for small shaks. PE Mysis is another good starter food for small catsharks. I used both with my pups when breeding coral catsharks.