You know the fact that the strong drugs seem to have little if any effect makes it sound to me like he has a serious energy blockage.
That would also explain physical issues too. Too bad there isn't any good acupuncturist close by. There are several natural type things that may help- Fresh Factors, yucca, arnica, DGP pills etc., even pressing on the "aspirin point" may help him. One thing that has really helped my houndies(and me) with pain from age(Aggie is almost 14) and injuries(Cash) and that is a BIOFLOW magnetic collar. It is so strong it is a class 1 medical device in GB and you have to get them from there. The cheap magnetic collars readily available are not effective to my knowledge. It really has to be a real BIOFLOW collar but let me assure you they work very well and have been most effective on the 2 dogs I tried them on. In fact it comes with a 90 day money back guarantee so you've nothing to lose by trying it. They really helped my dogs-especially Cash. Their web is www.magnet-healing.co.uk but I don't know how to do links so you may need to type it in. In fact if you pm me with an email addy I can send you 2 or 3 articles on this and pain options. Just keep trying and I'll bet you find something that works for him. Give him a hug for me! (gently)