I actually used to dislike Dumb until I met him at Roverfest. Out of ALL of the people, he was the nicest, most down to earth dude ever and now I'm a HUGE fan of his.
Honestly, I think he tried really hard to be civil with Andrea. Dumb had been miserable with Andrea for a really long time. Dumb wanted a divorce and he actually TRIED to divorce Andrea, but she tried to get him to stick around for marriage counseling. He tried that, and it still made him unhappy.
In situations like that, it's not fair to both parties to be stuck in a marriage/relationship where one is happy and the other is not. But Dumb tried, and he just couldn't do it.
Even after the separation, Dumb and Andrea were STILL civil with each other. They went to a concert together, and if Dumb's son missed him, Dumb would go over and be there for his son
As waco already stated, his soon to be ex wife is trying to use their children as leverage which is DISGUSTING and Dumb has every right to be pissed off about.
Also, on the show, have you been listening to how hard Duji has been on him lately? Everything that he says she will jump down his throat for. She's treated him like garbage and pretty much no one on the show is stopping her from doing so, so he has every right to be in shitty moods.