He is a black throated monitor (Varanus albigularis), and probably wild caught. He is also quite skinny for his species. Try feeding him more insects (they make up most of a blackthroats diet in the wild) and eggs. To help with shedding give him a deep soil or soil-sand substrate. I find that mixing in a little sand helps hold a burrow. Besides helping his shed it should also make him feel mor secure.