I think he sounds like a 9w1 to me. I'm not entirely sure, but I get the feeling that 9s really feel it when they get noticed because they don't feel like they exist. This is why it says in most profiles that 9s will work in the background to help others etc. Since they don't exist, they might have trouble knowing who they are, particularly in the eyes of others.
I think you should try not to convince him of his type, if he is a nine, he will probably just go with whatever you think, then revert back to what he thinks later, he'll probably say that he might be a 9 (emphasis on the uncertainty), but he wont be saying what he actually thinks, which for other people might be "hell no!". Best thing to do is to let him get a good feel for the type he thinks he is, find examples (preferably real people, lol, though that may be hard with types 4 and 5 being so rare) and let him uncover himself instead of revealing it to him. If he is a 9, he'll probably be open minded towards the idea of being a 9, but perhaps reluctant to make a definitive choice (as compared to an arbitrary choice or simply agreeing with someone else).
I find it never mentions this in the profiles, but with anger comes certainty. You can't be angry unless you're sure of intention or circumstance, you need to commit to anger, which can often cause a stir, which 9s usually wish to avoid. As a 9 that rids himself of anger, there's more drive towards forgiveness as uncertainty in intentions or motives is taken into account and the 9 assumes the best to avoid disturbing the peace or making a scene. Maybe that is in the profiles somewhere, but it feels like I'm just connecting the dots