I would be concerned that he isn't moving. Can you tell if he's alive? You might want to open it up and check on him if you can't tell. Sometimes you'll catch them right before they quit and can help them out, but you have to know for sure that they've absorbed everything first.
Checking that...
Can you pick up the yellow thing and take a pic while holding it? You can just put some paper towels under him. If the towel is smooth you can do that too though.
That little string shouldn't be a problem. Does his navel look ok? Keep him on a soft surface so he doesn't rip it open on anything. Don't cut it, it should dry up and fall off on its own.
Congratulations on the babies, fingers crossed that the rest of your hatch goes smoothly!!!!!