Men, why do some men act like this?

I moved in with my child’s father 2019 and got pregnant right away. At the end of that year I found out he was cheating. Covid hit and things got even worse between us. I moved out February 2021 to my own place. During the time I moved out I was allowing him to play head games with me and then I finally stopped. December 2022 he begged me to give him a chance again. He would show up to my house crying and trying so hard to show me he was changed. We started couples therapy and he was showing me he was changed. I stupidly believed this and moved back in with him March 2023 and we got engaged that July. He was mostly changed for a good amount of time but then slowly started going back to old ways. Last December I seen he was getting in contact with old flings. He tried to hide it but was not that great at it. I being in love with him tried to move past it and believed him when he said he would go back to therapy. He never did and of course me bringing it up started to become an issue. It’s like walking on glass with him. If I say something he doesn’t like or if I don’t agree with him he becomes an ass hole to me. He will get loud call me names but then 5-10mins later go back to normal. In August he broke up with me because he of the outcome from the damage he has done to our relationship. I have been a stay at home mom so I can’t just leave yet so I’m stuck for now. He says I have no time frame and doesn’t care how long it takes me to move out even if it’s a year or longer. He got upset with me because he still feels we should be doing family things with each other’s family’s even though we are no longer together. He wants to take me out for dinner just us no kids and is also asking me to show support him for him at an event he has coming up. I don’t understand this mindset of his where he is trying to play house like we are this happy family. I know we still live together but we are not together. He is already talking to old ex’s so I don’t see why he is trying to have me go on dates with him and go to any events to support him. Even more weird is after he has broken up with me he has been wanting to hang around me more than he was before breaking up with me. If I’m working out he comes and hangs out with me. If I’m watching tv he comes and hangs out with me. I don’t understand this logic. I’m heart broken and trying to detach and he seems to want to keep the attachment.