First of all, I 'advertise' Feliway Comfort Zone because it works. It is made for cases such as yours where a cat is super stressed and/or naturally timid or anti-social.
Don't knock it till you try it. It's great for animals with 'mental' or 'emotional' issues.
Second, used in tandem with Rescue Remedy (found at health food or supplement stores) or some other herbal anti-anxiety supplement for pets, I think you might see some amazing results.
It's not impossible for cats to be mentally unbalanced, I've worked with a few myself, but most of the time we find that it is an emotional issue.
Because you cat was not brought up properly by his real mother, he is confused about his place in the family. He wasn't disciplined properly nor taught other things that mother cats usually teach them such as how to be independent.
Basically, his instincts are telling him one thing but he's been taught something different. Some bottle raised cats don't seem to have a problem but we see that about 80 to 90% of them do have some issues.
Sure, a vet could put your cat on Prozac or Valium, but those drugs only treat the symptoms NOT the root problem. Not to mention, they have side effects almost as bad as the issue at hand. Prozac is expensive to boot.
If you can find a good animal behaviorist, they might have some other suggestions. I have worked with cats for almost 12 years now and have seen these problems first hand many times. For the most part, the Feliway seems to work fine by itself but some people use the Rescue Remedy to boost the Feliway's effects.
If you decide to trust my informed opinion, the Rescue Remedy can be used at a rate of two or three drops in the mouth once daily or added to water. It won't hurt any other cats in the household to drink it if you put it in water.
I wish you success!