Thinking back to the very first 3some here and the others I cannot remember any drama or serious drinking, as Sparkles said it is only when Viola is involved does Dana react badly so there must be a reason.
They need to have an honest conversation regarding boundaries, Dana is obviously unhappy with Chris fucking other women and there has never been even a hint that she would fuck other men.
She may be drunk but that is no excuse for his behaviour - grabbing her by the throat and slapping her! I think it was because she did not want him fucking Viola.