Yes, block off so he can't see out and so light can't get in. Obviously maintain a normal day/night cycle of light/dark. If the crickets are crawling over him it will add to the stress, I'd relocate him to a leaf and leave the crickets in the bowl. They are much happier on real plants so could be a good time to introduce one. That's about as much as you can do to alleviate new environment stress, but it does sound like this has been going on too long. Can you take a photo to see how he's looking?