Yup he does indeed look kind of stuned in growth and also he shows a juvenile coloracion, not what you would expect from a ig that old. But I beleave that with good nursing he will increase both in health and perhaps even in size. Here some tips Ive used many times in the past to bring igs back from the brink: expose him to unobstructed sun ligth as much and as often as you can and he wants to, even a 20minute daily dose will have marvelous results and if needed hand feed him to increase its apetite with super foods such as hibiscus, mulberry leaves, alfafa, figs, water cress, mustard greens, dandilion leaves, Malva silvestris leafs,mango,etc. Also for now I would give him zoomeds reptivite every other day. Give him also if possible daily ,water with a needle less seringe to help him flush out any waste he may have acomulated in its kidneys during the time he was bad treated