Well, that explains a lot of what is going on with him. He was emotionally stunted at a very early age and needs to go back to that age to figure out the whys of things. He needs to understand that none of it was his fault and when he can accept that, he will then start to grow up. It's going to take some time for him to accept that he could not change the past and what happened with his mother.

He did a lot of rebelling at a young age and it was a cry for help. A cry to attention and affirmation.

I hope and pray that his mother will finally realize her role in all of this and apologize to him for abandoning him, but she doesn't sound like she's one that will do that.

Dig deeper for patience. You might want to wander over the Midlife Crisis forum and read some of the postings there. There is quite a lot of information there that may help you along the way.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.