I'm about to break

I just can't anymore. How can people be so cruel? I took my husband back after he cheated on me while we were dating, and then go figure he had an affair with the same person after we got married and I was pregnant. Even writing it sounds so stupid now but if you've ever know a narcissist you know how convincing they can be. Anyways, found out about the affair, had the nerve to be mad and started seeing him through a whole new set of eyes. He's a horrible father. He's negligent. Not abusive, which in my state, is not enough to win custody and if I tell him to pay attention to his baby, he calls me a nag. He let my baby fall off the couch the other day and I took him to the emergency room, instead of calling me on his lunch break, he eats, then texts me, "any news?" That's it. Like really???? If my child was in the emergency room, I'd be calling out of work to be with him. Then I have the nerve to get at his indifference, so he tells me I'm a nag and leaves to go out drinking for the next three nights. Im documenting everything, but I'm afraid it won't be enough. He convinced me to be a SAHM, quit my job so I have no money and he has tons. He hired the best lawyer in town and is telling me he will take him from me. I care more about my baby than my own life. How can someone do this to another person? He can't even watch him for two seconds! I hate him!