Fiancé ruining my life...

I wish I had a way out and a way to pay my bills because I'd leave my psychotic fiancé. My family lives an hour away and on the weekend we would drive down and get my twin sister to come help with my two week old. She's such a big help when she's here, she folds laundry, takes the dog out, watches the baby, takes care of our 9 year old son, I mean she does SO much. Having baby blues and all she's a big help to have around not only physically but emotionally for me. 
Well tonight my bipolar psychotic stupid fiancé honestly goes crazy nuts because our older son said a bad word. He automatically blamed it on HER for no reason. He started yelling and threatening her and getting in her face even. He called her a bitch and said mean things to her and even said he'd throw her out. I'm crying my eyes out because I don't understand why he would do that. She wants to go home and she prob won't come back for a long time 😭 I really loved her being here and needed her so very much. I'm so so very hurt. I'm so angry. My fiancé is ruining my life.