I can understand why you might be very wary of getting back in contact with your father, it's a terrible situation that your family is in and it must be very difficult to deal with. The thing is, your dad is ill and he needs as much support as he can get so that he can overcome his drinking problem and as difficult as it may be for you to contact him, your contact might help him give up his drinking. The same goes for the rest of your family. Remember that your dad is going through something horrible and to give that up, he has to make the decision to do so to begin with and secondly, he needs his family to support him.
I know that you are protecting yourself from being hurt and to be honest, I don't blame you. He is your father though and always will be, nothing will ever change that. Think about what it might be like in ten years time, alcoholism kills people if it doesn't get treated, for treatment to work, he needs to be supported. I'm not trying to scare you but doesn't that make you think that as a family, you should all pull together and help your father get through this no matter what has happened in the past? He is entitled to a normal life, to get that he needs to realise that he has a problem and he needs you and your family to help him through it.
At the end of the day, you need to do what you think is best for you, you need to do that you are comfortable with. Start off slowly and see how things go, if things go well then increase the contact that you have with him and so on. Try to help him through this difficult time in his life. I know that you're scared of getting hurt but sometimes, in a situation like this, it can't be avoided. Do what you think is for the best though, if you don't know what that is right now, give it time and you'll figure it out.