Why am I taking his cruelty so hard?

I have a pfa order against my ex-husband. In that order he is allowed to be with the kids and have minimal contact with me concerning visitation with the kids. Well last night I went to a comedy show and he was watching the kids while I was gone. When I returned I had this odd feeling that he had been poking his nose in my business which is not unusual for him. He commenced to tell me how we need to try and work things out and I told him we were over then he made some snide comments about me kissing someone else and that's why I won't kiss him. I confronted him about going through my things and asked if anything was missing which he denied until I checked and saw letters and pictures of my boyfriend missing. He demanded the paternity of our youngest son be tested because my boyfriend made references to him being his son. My youngest son is three and my ex has always acted like he thought my youngest son wasn't his but I'm upset because to him this was the perfect opportunity to deflect responsibility. My boyfriend stepped in as a father for which I'm very grateful but I'm upset because my suspicions of my ex treating my sons differently are confirmed. I told my ex I will be happy to give him a DNA test but I can't help but feel furious because as soon as I didn't agree to work things out he didn't want to be father anymore. Am I wrong for being so angry?