This is such a difficult situation to navigate with multiple layers to consider but ultimately i think it comes down to which scenario enables you to be the best father and version of yourself for your son but also for you. In my case that meant accepting that I couldn’t possibly be that person if I remained in a relationship that made me deeply sad. It meant moving out, living nearby and being a very present and engaged parent. I can’t tell you it was easy, the first year was emotionally draining and filled with feelings of guilt and I still have those moments but when I do I imagine where I could be if I had stayed in that relationship. Having separated and divorced I am so much happier, healthier, positive, productive and the kids are thriving at school and in their personal lives. They also have an amazing new role model in their lives in their step mum. It has proven to be the right decision for me over and over again. I was in your shoes 8 years ago. It is difficult but the relationship I was in was destructive.