Why is my ex being an A** hat?

He's abusive. That's all. It's a power thing. He can't stand that he doesn't have you under his thumb any more. He paraded that women in your face hoping for a reaction from you. When you didn't give it to him, he tossed her. Unfortunately, affairs can be really exciting, hence the appeal. Its also fairly common that the relationship doesn't last once that fragile structure has been broken. As for being mean & seeing your family, well, he probably still has some feelings for you & he's probably angry at himself but he's misdirected that anger onto you so it's basically like he's tormenting you to make himself feel better. The same reason is most likely behind the picture thing. Just ignore his behavior. Don't respond or give him the reaction that he's looking for (otherwise he'll just keep doing it) & eventually he'll get over himself & stop. Good luck!