When they discover they've got a crush:
Ignores it and buries it, deep down to where it might never bother him again. He doesn't think he wants to take another chance on love, not thinking he's worth much as a lover anyway. It would really only work if the other person pursued him, because he just wouldn't think it was worth the trouble just to disappoint the other party.
How they confess/hint:
He would most likely confess only when he was inebriated, but there's no doubt there'd be hints about how he really cares about you. He's more likely to give into doing something for you, like if you need him to run into town nearby, and he can make a few slick comments that hint at an attraction to you (but are quickly blown off, or he acts like he never said anything at all).
How to win their heart:
It's not an easy task because it doesn't really have much to do with you doing anything in particular, though he does find someone with a kind heart rather attractive (even if it's hypocritical to think he deserves someone like that). Being honest with him earns bonus points, even if it's a hard truth, supporting him when he needs you there, and giving him the same love, respect, and loyalty he gives to you while in a relationship.
How to break their heart:
To make him feel like he's not good enough when that's already how he feels. To openly flirt with and lust after others while he's around (in a very uncomfortable way, he doesn't expect you to not feel attracted to other people). Cheating on him would be the biggest deal breaker and there's no coming back from it in his eyes, because he's very unlikely to trust you again after that.
Things that make their heart flutter:
Praising him. He would never admit it but being appreciated, being told he's things that he thinks he isn't, is something that really gets to him. He might even believe you if you say them enough. He also likes when he can tell you looked forward to seeing him or spending time with him.
Their type:
He doesn't really have a specific type of person, as long as they're not completely insane and do whatever they want with no regard for other people (especially the gang). He likes people that show a certain degree of loyalty, perhaps some softness towards humanity (it's a good balance to him, in his opinion), and, well... he does like a partner who's affectionate, specifically behind the scenes when you're alone together.
Goals in a relationship:
It really depends on how close you two get, and how long you're together. He never thought he'd enter into another romantic relationship and he did, but it won't be as easy to convince him to have kids in the future for obvious reasons. Marriage would be a little easier to convince him on compared to having kids, but remembering the last time he was engaged, he'd prefer you get married as quickly as possible (to prevent you running out on him? To make sure that it's real?)