I'm really not sure that shaving is the best idea...it could be itchy for him, irritating, and if there are scabs/bacteria it could break open the scabs and spread bacteria either way.
I'm sure a skin smear was done and/or a culture - -what was the result? Until you know the cause of these scabs and skin issues and fur issues, there is no way to treat him
.
It'd be really important to check his thyroid, has that been done? Are there ANY other symptoms, even random unrelated ones?