I think the problem was that your reasons for not thinking he was happy were all about you, or about things that happened twenty years ago. Ultimately, you seem to think he isn't happy because he visits his parents every week, threw some tantrums as a teenager, is not confident, does not take enough interest in you and didn't come to your wedding.
If he was genuinely unhappy you would probably be able to come up with an awful lot more than that and there wouldn't be the focus on how it makes you feel. Your anger about him not coming to the wedding has clouded the issue.
You need to think carefully about your reasons for believing he is unhappy. Try to remove yourself from it. Try not to attribute motives to his behaviour that you have no real way of knowing about. Look at the evidence as objectively as you can.
Then weigh how much of your anger and distress is down to you genuinely wanting to be close to him, you being upset that he's 'damaged' and you being mad that he has snubbed you, a confident, happy person who is accustomed to being liked and sees herself as 'unbroken' while he is 'broken'.
It is difficult for me to take your psychoanalysis seriously because if my brother was unhappy and I wanted perspectives on how to help him, I wouldn't have brought myself into it so much and would be genuinely thinking about him and how to do it. I wouldn't working on the basis that he's not giving me what I want (and this quickly degenerated to 'I don't like his behaviour'). On the other hand, if I was hurt and angry because he hadn't come to my wedding, I would have recognised that it was the time to own those feelings and how they might be affecting my behaviour to me (and thus negatively affecting the relationship), rather than pretend I was in a position to objectively analyse his 'issues'.
You seem too quick to say, 'Ah well, he's damaged, he won't have changed in the 20 years we haven't been sharing much, that means my behaviour will be above reproach and his will be all wrong, never mind - I can't do anything about it now but stew on the internet.'