Am I supposed to forgive him?

I got into a fight with the baby dad of my twins and it was over him cheating on me and we are not together and haven’t been for a few weeks but I had to borrow his phone. I had to borrow it for a thing with Facebook and he left his messages open with his ex wife, I saw my name and started to snoop. This asshole has been planning on fighting for custody of my twins so that she can be their mom, not only that but they had been sleeping together when we were together and even though I was at his house going to stay the night due to a fight with my parents she was going to come over and make only fans content with him. I know we are not together but we had just talked about getting back together before I saw his phone. Not only that but he was talking to her about where I live, she has threatened me since the beginning to beat me up, when I go to school and how I’m such a whore for sleeping with him so easily. Then it came to the part that broke me the most, the only reason he’s gonna fight for custody is because I don’t deserve to be a mom. We have a written agreement that he wants nothing to do with them and cannot fight for custody that has been noterized. I’m going to get a lawyer soon but I feel like I’m going over board.