This sort of black-and-white all-or-nothing thinking in terms of interactions like this is so damaging.

OP, I would suggest that when you approach the situation, you be clear about your boundaries and that the touch wasn't welcome, but understanding of extenuating circumstances. Something along the lines of: "You grabbed my breast when we were out drinking with the group. That was not okay. You won't be doing it again. If you don't remember, it was because you were so intoxicated at the time. I understand that you are going through a hard time regarding your father's health. However, that does not excuse your behavior. I deserve an apology and respect in the future. If this happens again, I will need to (outline steps you are comfortable taking)."

And yes, if he's an asshole from there, it's probably time to escalate things. But acting as if it isn't understandable (not acceptable, understandable) to act out oddly in the given scenario is deeply uncompassionate and reducing a person to "uncivilized" is just patently fucked up.