Help!

So I have been a single parent since my daughter was 5 days old. Their dad is a narcissist who is actively trying to cut me off from my family, still spreading lies that I’ve been sleeping with him and has taken the vehicle that the children and I had so we can’t get anywhere and has told me repeatedly don’t call anyone if you need to go anywhere you call me nobody else.
I am starting to get more comfortable being a single parent and I am feeling ready to get back out there in the dating scene. My daughter will be one in October and I know I want to have more kids but I am constantly hearing it from the children’s father that if I date anyone he’s going to consider it cheating because we were engaged and he considers that to be married so on so forth.
I’ve been talking to a guy and he’s also a single parent. He’s got an older kiddo than my son by just a couple of years we’re hitting it off and we really like each other. He is ready to settle down and commit and I am as well I am sick of going on a date with men that say they are ready to settle when they’re not they still want to mess around this person is ready to commit and settle. I know it’s none of my exes business of what I do in my home, but he is the kind of person that will make it his business.
I have custody hearing soon and I have high hopes that I will get full custody legal and physical, because of the fact that their father cannot take care of himself, and cannot take care of our children like they need to be I went into to preterm labor five weeks before I was due with my daughter because he had a mental health crisis refused to seek help has no respect for boundaries and didn’t matter if I told him I need a minute I need to relax, I’m having contractions. I could not relax, he would sneak out of the house and drive around when he had not been sleeping for 3-4 days at a time taking Adderall after Adderall to stay awake he is not a safe person around my children.
He assaulted our son by cutting off of his hair when I told him don’t do that we’re American Indian we have a tradition when he is ready to have his haircut and did it anyways because people were mistaking him for a girl he said, and he was tired of it. What do I do?!?! :(