Ending my 7 years relationship with an alcoholic (long story)

So I obviously wanted to vent and ask for my rights, as I been in a long 7 years with my boyfriend we have a 4 year old daughter and a boy on the way in 2 months. It didnt get bad until after we had our daughter, he still managed to work hard and provide for us but seems any time he has alot on his plate or stressing out about something he drinks uncontrollably that I feel as though anyone comes to say anything he just gets this look and always wants to start a fight with anyone. It's always been verbally abused with me when he drinks and I say something and he comes back and calls me name, it seems as weekends come he drinks as he gets up in the morning, and he drinks those tall single 8% beer and will have at least 2 or 3 of those sometimes I find little airplane shots too. He would go through this drunk stage and then pass out on the couch or bed and the next morning want to say I'm sorry and we will have a better family day today and no drinking, but somehow he always seems to get away with it, he does tells/ask me he getting one beer. Sometimes it will end to want more and I would say no and he will find a way to say hes not drunk like he used to be and start a fight with me. As I know how he gets he finds it offensive anytime I say about him wanting to grab a beer on our way out for errands or family day. I feel as those he feels he needs to drink as to have a good day and finds every excuse as one beer is not bad as how he used to drink. I am a stay at home mom and live 4 hrs away from my friends and family, I have no car, no job and just feel I dont have support. It's sad to say I feel I stayed for my daughter and now we have a son on the way I'm at a point of leaving. Hes that type of person that his daughter means the world to him and when he drinks or we get in an argument he would say hes taking me to court to have full custody of her and what not and that I don't have a job or anything to provide for her, I dont know if he said that to hurt me or what. But I'd be lost without my kids, I been the one taking care of her 24/7 and when he drinks she sees how he acts crazy. And I'm afraid with us splitting up that he will have her and do his drinking or leave her with his mom all the time and let her take care of her while he goes on his drinking rampage or whatever. I'm afraid he will drink to the point he can't control and his daughter is in his care. I am the one to not want to take her away cause hes a great dad to her when hes not drinking, he plays with her, provide everything she needs and all that of good parent but sometimes his drinking gets in that way hes a total different person. I want to co parent the best but I feel thought he will never get better, even though he told me he wants help and not lose his family and that he wouldn't know what to do if we left. So that's why I feel I gave him chances over again cause he said he will get better but then I feel that with me never leaving jes comfortable with it and takes his drinking as advantage. Let me know what I can do, with the whole working together as parents but separate. Do I need to go to court to solve this and get an agreement? I don't what child support but co parent and help what he can and which I know hes willing to. I just dont know what to do, like I want more time with my kids because I'm worry of his drinking if hes ever alone with them. When he drinks I've always been around with my daughter so just the thought if I was to leave she will be in his care