well to start what are the temps of the cage, and what's the humidity.
keep trying to feed him silk worms but don't force feed. force feeding causes lots of stress. if he is over 12 in. the mill worms should be fine but don't over do it. freshly shed mill worms were a favorite of mine when they were younger try some of those.
don't get discouraged and keep the posts coming and let us know how its doing