Physical Affection: Go for it. More likely than not the reaction will be more awkward than warm.
Flirting: Please. Step cautiously if playing post s3 (see below.)
Violence, fighting, and injuring: Sure thing. For longer, more drawn out fights, let's talk and figure out specifics including any major injuries.
Death: He's harder to kill than most, so we do need to talk.
Mind Reading: Sure. PM me if you want specifics about what's going on in his head.
Ships: this man is a bisexual disaster and we all know it. I ot3 the main trio to hell and back, with the general assumption that earlier on in the relationship things are easier with sypha around because treffy and the dhamipr are not gr8 at emotions immediately

as of season 3 I am open to exploring what's up with Taka and Sumi before everything goes to shit, but I am inclined to be cautious.
as of season 4 I am open to exploring whatever comes with Greta, but I'd rather that in the context of an ot4!

Also as of s3, if shipping means sticking to canon's course of events, we'll need to address Alucard's new found trust issues around romantic and sexual relationships. Never mind no kinks for this man yet.

Backtagging: Yes!
Threadhopping: Very yes.
Fourth Wall Breaking: Please do not.