What behaviour should I expect from a recently dumped guy?

I’ve started a relationship with a guy who was dumped two months ago by his partner of more than 15 years. We’re seeing each other now for about five weeks. He seems in a urge to introduce me to his friends. Last weekend we finally went out with one of his pals and his girlfriend for five months. He got drunk and ignored me throughout the night, refusing to dance with me, paying exclusive attention to the his friend’s gal, whispering sweet little nothings to her ear, mouth feeding her chocolate mousse with sensual mannerisms… He apologised later stating however he’s being in trouble before for being “flirty”. I guess the question is, shall I withdraw completely so he can affirm his masculinity with others? The problem is, despite his behaviour, I’m totally smitten with him. I guess I would like to hear from recently dumped people about what behaviour should I expect.