What are your opinions

My boyfriend and I of 10 years (not married) have problems in our relationship due to his drinking and his cousin. They hang out all the time and stay out late. It used to be every single night. Now I know every once in awhile is okay but it’s all the time. They drink and drive and my SO knows I’m not okay with it. We argue every time they hang out. My SO acts like his cousin when he’s drinking. His cousin isn’t really a good person and the worst husband. My SO puts me down and treats me like shit when they’re together so I told him he needs to stop hanging out with him and he told me he’s not going to. He told me I’m over reacting and being irrational but I feel like my feelings are pretty valid. I feel like if you know what/who is causing problems on the relationship then you need to let it/them go. But I feel he’s choosing him over me. What do you think? Am I being irrational ?

I want to leave and he knows I do… I don’t have any experience in work.. I’m a stay at home mom of our two. One has disabilities. We can’t afford child care and don’t trust anyone to babysit. But he’s threatened me to take my kids away and said he won’t help me financially until I figure something out.. I know it’s an excuse but I’m so scared..