Oh my goodness, you sure have been through a lot. I want to say that I'm so sorry you have had such painful things happen in your life. Now, this is my firm take on it as a mom. I'm not a mom of teenage boys. As they reach the teenage years, hurts and pains of the younger years begin showing how they emotionally effected them. It can be sad to see it and wish we'd known 'back then' to change some things as the damage is already done. This is one of those cases. You know on some level that your boy needs to feel like he is loved by EVERYONE he lives with. It hurts and it sounds like you may have been dependent on him for giving you a stable financial situation, a home, and a sense of normalcy to family life. But it's not normal for real if part of the situation was his making your son feel less than, unloved or like he didn't belong in the home he was living in because you chose it. I'm not in any way meaning to sound harsh. I totally understand and get where you are coming from. Your number one job as a parent is protecting your kids and that includes caring for their sense of self. You SHOULD have full custody of your son because your ex is an abuser that resorts to physical violence. Now, you've gotten with a man that is cruel. To your child. This is all a vicious cycle. I'm so sorry. And wow, let me tell you this painful truth . . . the hard years with your son are coming. He hits 15 and 16? All bets are off. He will be even less charming. He will be even harder to deal with. He will rebel. That's what they do and it's actually normal. But HARD. So, this could be a blessing in disguise if you were with a man that doesn't deal with your son AS IS.
I'd see what other living situation you can manage. Is that possible? Do you have any support? Do you work or are you stable on your own financially? Down the road, wouldn't it be wonderful to have a man who loved and accepted you AND your kids? That's what you need as a parent who loves her child. That's what your child needs. If you want to be with an A hole who isn't going to be loving toward your kids, you can do that when they are adults and out of the house. But for now, you have to create a peaceful home for your kids, all of them.
I am hear to talk to you because I know this isn't easy to deal with. Probably isn't easy to hear either. You have been a victim of abuse. You may have had some situations prior to that as well that shaped you. And that means that your thinking gets a tiny bit warped. And the situation you've been in IS better than when you were with a man that beat you. But, it's still not ideal if he doesn't love your son. Big hugs to you, sweetie. We have a relationships forum too that has some regular posters that you could talk to.