I honestly don't think you should embark on heaps more behavioural changes until he has been fully checked out by a vet. Sounds like you have already done so much - and the thing is if he has a condition which he may well do, then he will be feeling it, and not happy. Many health issues can...
Hi, it sounds ghastly for you. Have you tried talking to a vet - taking him in for a thorough check? It is possible that he has a medical problem (which can definitely affect behaviour), and it would have worth having some blood tests taken. It would be good to have that ruled out before making...