Please keep in mind I am not a physician, this is for entertainment purposes only and you should consult your physician before changing or engaging in any therapeutic program
I am sure he has lowT as well, he has all the signs plus he is on oral meds which are notorious for lowering testosterone.
It is safer for him to get on therapy right away, keep in mind he is doing it at this point for health reasons, so although working out will help his program it is warranted wether he works out or not. Think of it as someone who needs adequate amounts of T just for normal daily duties, aside from correcting BMI wich is a pleasurable side effect.
No restart for him, getting what little he could possibly make to return at his age is not worth it. It is supplementation time, and at his age GH optimization would be important to ward off any intrinsic diseases in his future.
It is also important to note that diabetics who take insulin normally need half there normal dose once they start TRT.
Hope this helps