Don't try to fix him. You don't know him that well. Best you can do is treat him kindly, as you would anyone else.
I know one person who has a mental handicap of sorts and exibits some of the same behaviours. She has schizophrenia, has a second personality, and a witty humor when it can wind its way through the madness. She's lived this way for over three decades and there's nothing I can do to change her.
I also knew a man who was trapped in his own body my a neuromuscular disease. To some onlookers hed be labeled as that "poor cripple"... Not my words. But as I worked with him I learned of a man that seemed to be well read and funny as hell. But you had to know where to look for the real person inside.
The person you are describing is more functional concerning the "real world" than the ones I'm describing... But the point is, it takes all kinds to make up the world. Best you can do is hang around him, pay some attention, and maybe make some connections. Your concern is reasonable, and your wanting to help him fit in better is out of good intentions. Id still hold off on trying to fix anything about him.
Again, as long as he's treating you fairly, you should do the same... Maybe you'll know some answers in time.