Mark, it's really hard to say whether you overreacted or not based on the little info you provided, was she telling you she was keeping the boys a few extra minutes, hours or an extra day or what? Was it inconveniencing you in some way or was it no big deal, but you blew up over it due to your frustration over your whole situation? I suspect it's the latter.
I'm sure he tried to explain that she was supposed to have them for the weekend only and then decided to keep them for several more days. Not politely asking but insisting/demanding. I find it rude. And I get why that sort of behavioir frustrates Mark. He appears to have been more friendly towards her than most others toward their cheating exes, and being stomped on a little bit more is the reward.
