Sisters abusive boyfriend/baby daddy😞

This is long so bare with me.

So little back story I pretty much raised my youngest sister. My mother was diagnosed with lung cancer when my sister was 11 years old and I was 18. I already had a 2 yo son as well. Anyhow, shes just like a daughter to me. Shes my sister but theres nothing like the love I have for her. I want to protect her. Make sure shes happy and safe always. My mother went into remission btw. Shes much better now. Well, my sister met her now boyfriend. At first he seemed charming. Dont they all? The first signs we saw was he couldnt hold down a steady job. Would make excuses about how someone was "bossing" him around, or the pay was too low. I grew up watching my father abuse my mother until I was 12 so I know the typical signs. Well my sister fell pregnant only after being with him 3 months. We were all overjoyed! I was so happy for her bc I knew she would be a WONDERFUL mother. it felt kinda fast but she was in love and happy which made me happy. they have a handsome, smart, son. Hes 3 yo now. Over the past 3 years he has hit her, went to jail, gets out and she takes him back. I get a call just a min ago from my mother. shes freaking out saying my sister called her and said he hit her. They began to argue and she shoved him bc he was in her face and he slapped her. She managed to get her keys and leave. I must add he struggled with meth. Which made him mean and angry. Hes been "clean" the past 6 months. That's what he tells our family and her anyhow. He lost his mother last year (they were veryyyyy close) and since then it's only gotten worse.

But my mom proceeded to tell me that my sister is driving around and doesn't want to come to my mother's house bc he will just show up & she doesnt want to have to call the police and get him arrested. I told her she can come to my house hes never been here so he doesn't know where I live. My sister told my mom she would sleep at a truck stop with her son just until she knows he was calm. So needless to say as a mother my mom is worried. She asks me to call her and let her know what my sister is going to do. So I get off the phone and immediately call her. 2 rings and he PICKS UP! I'm like "hey is (my sister) there?" Hes like "Yeah but shes in the bathroom at sonic." I said "can you have her call me back?" He of course says yes and hes acting all gitty like nothing is wrong, which is what he always does infront of my family even minutes after he hits her. I called my mom back and my mother is still worried. My mom had five kids with my abusive father and she saved enough money to get us out of the state and away from him but it did take her 12 years to finally get sick of it and thank god my father never accidentally killed her by beating her. My sister though knows her relationship is toxic. She has left him several times and come to one of our houses and the moment her baby daddy comes begging and pleading she goes back. I always tell her "don't say your doing it for ur little boy bc if you think for a second that's better for him, watching his mother and father fight and his mother get hit you are wrong." I just needed to vent. I know I cant physically make her leave him. All I can do is be moral support and pray one day soon before it's too late she'll come to her senses and leave for good. I just cant see it ending well. Sometimes you just want to help but just like having someone you love addicted to drugs or alcohol you can't help them, they have to WANT to help themselves. I just hate it. The feeling of being utterly helpless.

I hate that he lays his hands on her and she continues to forgive him. 3 years of turmoil. The past year has just been HECTIC and stressful constantly worrying about her each time she calls crying and upset. She just started going back to school to become a RN. He doesn't work, doesn't watch their son (my mom baby sits.) She got a job working part time at an assistant living center and shes an amazing mother, but shes so blinded by the fact that she has a child with this man she wont leave. She has LOTS of family to go to. Lots of support. Many women dont have that when they are in an abusive relationship. I just wanted to vent. Thank you ladies for listening.