I heard about the guy with the chicken necks. You just have to chop them really small.

I know you are getting a lot of suggestions from people, a lot of good advice. Natural sunlight is best. If you can get a mercury vapor bulb, that is second best. If you keep with the 5.0 bulb, then it needs to be inside the cage about 6-8" from the basking spot. A 5.0 is not very strong, though, and not many people recommend the coiled/compact lamps.

He needs proper temperatures to keep his metabolism up, so the basking temp needs to be 110-115 and the cool side low 80's with a night time drop into the 70's.

As for diet, the calcium to phosphorous ration needs to be 1.5 or 2:1. When something is out of whack...diet, UV exposure, vit D, then calcium metabolism is out of whack. Calcium is utilized by the muscle fibers and the nerves for proper muscle contraction. When calcium is low (or high), then the muscles cannot function as they should and that twitching is seen. If the blood levels of calcium are low, then the body must get more calcium for the muscles to function properly (the skeletal muscles and heart muscle), so it turns to the bones for more calcium. Without bloodwork from the vet, we cannot say which component is affecting your tegu. Otherwise, we just sort of recommend everything, but we aren't vets. Ground beef is really the same as ground turkey, as long as they are lean. It's been a while since I've seen the chart, but the ration something like 1:33, hugely in the wrong direction. Insects are anywhere from 1:12 to 1:30, unless you gut load them or use some that are naturally higher in calcium and have a proper ratio. That's why it is so important to supplement with a good calcium product that does NOT contain phosphorous. Usually it says so right on the label, and the directions for use will be right on the label.

If he isn't eating, then I would get some chicken stage 1 baby food. Take a tiny baby food jar, and add 1/2 teaspoon of calcium no phosphorous with Vit D. It is based on 1/2 tablespoon of calcium per pound of food. You could even add just a bit more, but it may make the food taste too chalky to be appealing. Then make sure he has good UVB, and see if will improve in a day or two.