I'm pissed, he says I'm overreacting...what would you think if your partner did this?

He sounds like a d**k. I don't care if he thinks he's hot, you deserve to be treated with respect and if you feel uncomfortable or unhappy about something he did, you probably are feeling that way for a reason and your reasons are valid. And, if he is talking to his ex-gf in the manner that he is and they just broke up a month ago, i would be suspicious of this behavior.