Can’t deal with him anymore what do to?

I separated from my bf about 2 years ago we were high schools couple had two beautiful babies.. well k broke up with him because he cheated on me.. well I loved out and live with my parents while taking care of my 2 year old boy and 4 yearnold girl. Well we been this constint argument about my kids.. he never really seems to care about visiting them dos er provide for them . I’m the full time parent. He’s on child support but nuthin. He has tried to convince me on taking it off he gas promise to varias times hellbut change and be a good father. He isn’t so there was a time where when he apperared and wanting to see “ his kids “ like once a month or two I would say no. We would talk it out and he did promises me believing him let him see the kids cuz I know. As a mother they need there dad in there life. I never had made a big deal . No I eh thou . Again we’ll fight over him telling me what to do how to take carenof my kids and stuff. He would stop coming . I even was gunna take him off the birth certificate and make me the only guardinship . He agreed he only cared if I was going to cause trouble for him he was willing to sign the. Over .. then he came out that no because his family found out and got him in trouble week again we talked. We’re even got lawyers. He wanted my kids supposed to him k needed to move on. Like dude I been moved on just cuz I’m single doesn’t mean it’s because I’m missing g you cuz tbh I have fuck kiddies and love being single and well he gt with the girl he cheated on me with.. well we decided he promised he’ll be in the kids life give me money and all that well. He did for two months straight until tax season came i told him he was stupid for asking about putting the kids on His taxes .... if I was working full time. And providing for them. He hasn’t come to see them hasn’t gave me money which to him is 80 is enough for them.. there sister in law has seen The kids and taken them but they live together so i dont know what to do anymore.? Like do I tell her no because of this. Guy would think I don’t gotta see them because my sister I. Law brings them and should I just fight for full custody . Take him off there certificate . i dont know what to do?! I don’t want my kids growing up hating me thinking I took there father away from them and I know I won’t tell them what happened between there dad and me