So the thread about dredging up old threads led me to find this, which I had totally forgotten about. Later today I will update post #1 with a treatment that could have been tried.
He did die that evening and I convinced his owner to weigh him and do a necropsy. Body weight was only 1200 grams. Normal weight for a male this age is 2400-3200 grams.
Here are the necropsy pictures:
This shows how thin he was
Classic blackhead lesions