I'm sure the more experienced crabbers have a lot of questions for you.
First, I'm concerned that you put him in iso and he hasn't got his exoskeleton to eat. I'm not sure, but he may have come up for some fresh air, but left his exo down underneath and he needs to eat that to help build his new exoskeleton and help it harden.
He should be left undisturbed, just make sure he's got a fresh dechlorinated bowl of water and an ocean salt mixture bowl of water, as well as some high energy foods and high calcium foods. One mixture I've seen mentioned is organic honey and crushed cuttlebone.
My post molter is eating that as well as flax seed meal (ground flax seeds), which have important oils in them. He is getting organic peanutbutter (protein) and egg yolk (protein).
Also, make sure the temperature and humidity in the iso are at the desired ranges - namely 73-80 Degrees and about 70% humidity.
One of the most important things once these are all in place is that you do not touch, hold, or otherwise disturb your post-molter. His energy stores are depleted and he needs to be stressed as little as possible.
You may have made a mistake moving him into iso without his exoskeleton, but it's a good thing you are here asking questions. You will get the help you need to take the best care of your hermit crab.
Edit: A question has occurred to me: Why did you iso your crab after his molt? Were the other crabs being threatening to him?