13" is still a baby big time and typically are more skittish than adults. You want to make sure you do not stress the little one out right away. He needs to acclimate to his new surroundings and to you. Start of first by letting him be in the new cage for a bit without harassing him. Then slowly progress to just sitting/laying next to his cage so he can see you and get use to you. This may take a week or so. Next you can start petting him, or attempting too. One thing that has work to first have your hand palm-side up and reach for him at an equal level. Babies in particular can get spastic if reached for from above in thinking it is a predator trying to eat them.
My main concern is that he is eating on a regualr basis first.
You can slowly porgress from here and let him roam about. Do not try to suppress him in your lap at first, this will come with time and as he gets older.
I know all too well that patience is need with tegus and it is hard to control! :0)
Potty Training? Some one on here (I can't remember if it is Rollin or someone else) was having success by using the tub with water (they typically will poop in it), then moved to the tub without water, then moved to newspaper in the bathroom.
I have been slowly working with ours as well using newpapers, yet they still prefer the carpeting. LOL Not a good thing! LOL
Good luck!!!
Greg