The less spunky and the no sheding is form the natural instinct to hibernate. They naturally slow down, sleep more and stop eatting. Becuase they are not eating they also are not growning, no growth means no need to shed. I do not think this is linked to the early condition.

As for the shed still stuck. What are your humidity levels? Soaking works but it also drys out the skin. Try making a humidity hut, somthing that fits in the cage that hold humidity well, that also has a enterance for the tegu to come in and out of. I use a rubbermaid containor filled with moss and coconut fibers.