Always listen to your child. Children see things that you don't until it's too late
You said: he sees his son twice a month, he doesn't pay maintenance for him, he doesn't work, he's on disability and has no intention of going to look for work. AND he is not getting along with your child. What is attractive to you about this man? With so much to be truly concerned about, maybe he isn't the best choice in boyfriends. He's certainly NOT a role model for your child. I feel like you can do better. You care about your child, have had a mature break up with your ex and get along with him now, etc. What about throwing this fish back and finding someone that is better suited for your family life? Or your life in general to be an equal contributor in the least and willing to take care of their responsibilities. I don't think I could take any man seriously that didn't at least pay child support for their child. Start over hon. Move on and find a better match for you AND your son. good luck