"He Cheated On Me & He Impregnanted My Cousin, But Now He Wants To Marry Me"

I have been with my baby daddy on and off for 6 years.
He is a great man. He treats me and his kids great, but his cheating is the reason we are on and off. I love him to death. He is the father of my children, and from time to time we fight. Yes, he puts his hands on me. I know that he loves me and he doesn’t mean to. I provoke him to do those things. I can deal with the fighting, but the cheating, not coming home and not answering the phone when I call at 4:00 am or 5:00 am, I CANNOT DO.
I left and was gone for about 3 months. One day I went over to pick the kids up (yes his car had gotten repossessed), and my oldest opened the door for me and told me their dad was in his room. So, I went to
the back, and opened the door to find him and my FIRST cousin in the bed. TOGETHER! I must have lunged at her full speed and dragged her into the restroom. I beat the -ish out of her there. I got my kids and left. A few more months down the line, needless to say, I went right back to him.
After we got back together I found out I was pregnant again and he made me have an abortion. I started getting depressed. Then I found out that he was back sleeping with my family member again. AND SHE HAD THE BABY!!! But, I love him so much I can’t let him go! He’s even asked to marry me! I said yes, but I’m still not so sure about this. I really love him and I really don’t know if I want to go into a marriage with all this on my chest?!?!?!
Will I be able to forgive him, and for all that he has done to me? He has another child by my cousin, which makes my kids and my cousin kid double cousins. I don’t know if I can take this, but I can’t see him with no one else. I really don’t know what to do. People talk about me behind my back. I don’t have many friends because they said that he has tried to talk to them. I never believed them I have no one to turn to. I’m so stuck in love. Please help me! I need advice. I love him but I know I can do better without him!