Do you have anything from your old place that you could put in the cupboard with your kitty to make it smell like "home"? Like, does your kitty have a kitty bed, or blanket, or anything like that? That may make him feel more secure. You could also place some of YOUR worn clothing in there with him.
Most articles I've read suggest setting up a "safe" room; a quiet, small, out-of-the way room to keep kitty secure after moving. It sounds like kitty has made the cupboard his safe room. Adding some articles with familiar smells might help him relax a bit.