Backdating: Things with me can drag on for a long time due to timezone issues, so this will be invoked a lot.
Threadhopping/jacking: Ask the muns involved first, please.
Breaking the 4th wall: Stuff like "Hey, you're from Japan" or "you're one of the Dragons of Earth and I know your biggest secret" are okay, but please, nothing about him being a fictional character.
Hugging: Go right ahead. He likes physical contact, so it wont bother him at all.
Flirting: Expect him to flirt right back ;D
Kissing and/or other intimate actions: As long as there's been some good CR between characters, I don't see why not. He may enjoy physical intimacy, but there are limits to that and he's got some trust issues.
Relationships: I'm all for him to have a lover or a boy/girlfriend, but it may take a while to actually get somewhere good, because, like I said, trust issues, and the fact that he's a right bastard when he gets down to it. He's not like any other person, and he doesn't fall in love so easily.
Violence: Yes, you may pick a fight with him, but I wont guarantee that he'll lie down and take it. He's dangerous enough as it is without forcing him to raise a hand against you.
Anything else: Any questions/clarifications? Want to plot? Hit me up!