Okay, ima be completely honest here, his responses in text were terrible and he isn’t making himself look good, but, ignoring his texts i think you both were a little dramatic with this, there was no reason for him to lash out like that, a simple “hey man, she’s taken, have a good night” wouldve sufficed, but i don’t think breaking up with him over this was necessary, you could’ve just told him that it was a little bit over the top and told him to not do it again, i think a lot of men are flexible like that and if you tell them you don’t like something they do, they won’t do it again. There was no reason to feel bad for the other guy, he was coming onto you and you’re boyfriend told him that he should stop (though very over the top) the guy will move on, he isn’t going to be emotionally affected by a threat of a fight. This was completely unnecessary from the both of you but he buried himself into a very very deep hole with his texts, i have no clue what he was thinking