Hi, I'm 14 years old and I live in Queensland, Australia.

My mum and dad have divorced. I don't want to see my dad anymore because he is a narcissist and he has physically abused me and my younger sister. My dad now has a fiancée, who I hate because she's also a narcissist and a rude person. My dad has never done anything for my family, even when my mum and him were married. My dad and his fiancée don't care about my younger sister, who's 10 and myself. I love living with my mum and her boyfriend. I'm at my mum's house every day/night except the days/nights, that I'm at my dad's, which is 4 or 5 nights a month. My dad is also an alcoholic and so is his fiancée.
Can you please help me? Any advice?

What does your mom say about this arrangement with your dad? She is the only one that can change things until you and your sister come of age and can speak for yourselves to a judge in family court, which can also be sooner depending on your maturity and judgement.

https://www.qld.gov.au/law/crime-and-police/abuse-family-matters-and-protection-orders/child-custody

You really need to talk to YOUR MOM.