Most of this sounds a bit intimidating, but can be summed up as "if you're going to have your character touch, injure or otherwise attack mine, I want us to talk about it first" - that is, standard RP etiquette applies.
Threadhopping with this character - yes, no, or what? Usually, I'd rather not. If there's an IC reason for it, PM/IM and I'm likely to say yes.
Hugging this character? Ask me first. He's likely to tolerate it to varying degrees (from the very unlikely he'd-appreciate-it-if-he-weren't-so-uptight to the much more commonplace Icy Stare Of Death And Permanent Grudge, depending on who's doing the hugging), but I'd like you to check in first.
Giving this character a kiss? As above - though he'll tolerate this a lot less.
Other Things That Go With The Above Two Categories? Really, really, ask me first. Especially if it's going to be approaching NC. Yes, even in crack/capslock mode. Yes, especially if he's incapacitated. A few people have come onto him very strongly when he was (a) age-reversed, or (b) unconscious, and this squicks me, the mun, seven ways to Sunday. Don't do it.
Punching this character (provided they are given an opportunity to fight back) Check in with me first, but other than that, absolutely! I approve of trauma. He's likely to get seriously unpleasant if anything happens to trigger his batshit response, though.
Maim/murder? I approve of these - but, again, let's talk about them first. He has kind of a back door for death, being already dead, and in the Mansion Of Nobody Dies to boot - but any maimage, he's going to be stuck with until something heals him or kills him.
Is there anything you DO NOT WANT MENTIONED near this character? No! Shoot for the moon. There are plenty of things he doesn't want to talk about/hear about, though - his epic failure being top of the list. And good luck getting him to talk about ... anything, very much. I'll take most opportunities the mansion offers to make him run his mouth involuntarily (for great trauma; sigh, Light. get over it, etc.). Feel free to take full advantage of those.
Is there anything you need us to know about interacting with this character? Special physical features, fighting abilities? Please include information that other muns should know that your character might not say themselves He tends to either lie, or say nothing - or nothing of meaning. Though this isn't always the case, sifting the few facts out is more trouble than it's worth.
He won't usually initiate a physical attack - but likes to think he might. That's to say, he might fantasise about your murder, but he's unlikely to follow through on it, because there's a lot he can do without ever getting his hands dirty, and he has a realistic idea of his combat abilities. If he is attacked, he's not untrained and will do his best to defend himself. He starts as a dirty fighter (he's physically lightweight, though on the heavier side of the usual cast) and as above, if something tips him over into batshit, he'll want to get extremely dirty and aim for permanent maiming or disability. (sigh, post-death trauma) Obviously, asking first goes both ways. :) Anyone with decent combat abilities (the average Mello, for instance) will beat the crap out of him easily enough.
Anything else? Please mention it here. If in doubt, ask. I don't bite. :)