I’m so very sorry that you, your sister and your mom are living in such an unpredictable and hostile home. Alcoholism rarely is solely the problem of the alcoholic. As you so clearly pointed out, it takes its toll on everyone in the family. If you haven’t already, please look into whether there is a chapter of Al-Anon or Alateen in your community. These organizations provide important support and information to family members of alcoholics. I think you would find it helpful to go to a few meetings to see what they have to offer.
To make it through the year, I can only suggest that you and your sister spend as much time out of the house as possible. Keep your grades up and build your resume so you can get into a good college. Get involved with after-school activities. Volunteer at something you find meaningful. Take on a part-time job. Do homework at school or at your local library. Above all, be a loyal friend to your friends. You need people to hang out with so that you can give and receive the emotional support that good friends offer.
If you can, see if your mom will take you and your sister on some trips this summer to visit colleges you think you might want to attend. Then be sure to see your school counselor right away in the fall to start working on applications. There are many, many good scholarships out there but it takes time to do the research to find them and to apply.
An active and meaningful life with friends and at school will help you manage the stress at home. Sadly, you can’t change your dad. (Hopefully at some point he’ll want to change himself.) But what all three of you (you, your sis, and your mom) can do is build a good future for yourselves.
I wish you well.