My dad is a violent alcoholic, what advice can you give me?

I am 15 years old and my dad has been an alcoholic ever sinse his father died and that was a year before I was born so I have had to put up with the excessive drinking all my life. My mum finally got the money to move out 2 years ago but his behavior still haunts me. I wish I had more information about the effects on the body because of alcohol and excessive smoking because I am so afraid that he might die. The psycological aspects of growing up with an alcoholic man has really taken it's tole on me and my family. It has always felt like a big family secret all my life so much that my grandad didn't know until we actually moved out, even now I feel so upset and so angry every time I think about him. I can't bring myself to tell my bestfriends. My brothers and sisters don't understand how I feel as I am the youngest and witnessed alot more than them at a younger age and as they abandoned us in the end. I find myself terrified of him when we go visit and he causes a new argument but it is not only with him it's also when other men raise their voice I just don't know what to do because I just don't want to stay like tis forever. Can anyone give me any useful advice please? It is very much apreciated.