We have all gone through the same thing forgiving our alcoholic parent. Welcome you have found the right place, we understand totally. I hope you will try Alanon and really research the forum right here it will help a lot.
My alcoholic dad moved us a lot. I was in 10 schools by 10th grade and we moved 4 times before I started school. (The up side is I actually know every single neighborhood in the metro area! ha ha) My parents stayed together till the very bitter end.
You are a senior and ready to start your own life. The best thing you can do is to move out as soon as possible, going to college? Live in the dorm, figure the room and board as part of your loan for the first year. The second year you can apply for Resident Assistant, RA, then you can get it free. Please focus on you and not your parents now, this is your life now. They have chosen their life.
It seems like you think a divorce will make it all better, it won't. There are a lot of issues with codependency why your Mom is still with your Dad, not just finances, and you can't fix that. A divorce won't fix that. Only your Mom can fix that. You have to take care of yourself, get free and get healthy. Then maybe your Mom will wonder what's up and follow suit. Even if you could fix everything, it's not your job, your parents have to find their way or it won't stick.
We have a saying here that is the Three C's:
You didn't Cause it
You can't Control
You can't Cure it.
Alcoholism is not something he can just chuck like that. He will have struggles and it might be a long road to get things worked out. My dad drank till he was 80 and finally incarcerated with court ordered AA lock up treatment. Only then did he quit. Please do not put your life on hold trying to fix this with your parents, it could take a lifetime.
Now for forgiveness. You are very mature to even be tackling this now, some people wait a lifetime to do that. Congrats. However you seem to mixing up forgiveness with trust. Just because you forgive him doesn't mean he won't let you down again, he surely will because he is human. Forgiveness is for you, not really for him. You need to let go of the bitterness because it can change who you are meant to be. Forgiveness will not change him, it will change you.
It was the hardest thing I ever did but I'm glad I did forgive him. Then years later as I matured I had a simmering hate for my Mom allowing us to live like that. Had to work that through and forgive her too. At first I saw her as only the victim but she really was a willing accomplice. We have a thread that explains how we have dealt with forgiving our alcoholic parent here:
http://www.soberrecovery.com/forums/...ve-her-no.html
Please keep in contact, we are here for you. Good luck, praying for you.