My dad basically bashes my 2 sisters and i and my mum is too scared to do anything i really need advice please?

Im really sorry this all sounds very terrible. You should speak to someone about this since you are underage and you are not really able to do anything or defend yourself so you should look for someone to defend you. Maybe talk to your boyfriends parents and ask them to help you get help from someone. They could easily come and arrest your dad which i think is what should be done. I know about the reason him not wanting treatment on muscular dystrophy because my friend has it and he goes through temper tantrums and flips out in public and breaks everything. So i really feel for you. I really hope you find brighter days in your future. You should write a book about your life.