I'm about to graduate high school and I'm terrified to leave my emotionally abusive father and handicapped mother alone. Please help!

I'm eighteen years old, so I know I'm a legal adult. But at the same time, most counterparts my age have never had to wipe their mother's behind because she went to the bathroom on herself while they were at school, or pick her up off the floor at 2am the night before the SAT.
Over the last four years or so I've seen her health, wellbeing, and spirit shrivel away. She is 64 years old. All my life she's struggled with A LOT of health issues including diabetes and an array of depression problems. In recent years, it has become much more severe. She had several months where she was in so much pain she had to go to the hospital regularly, but neither there nor at her doctors' has anyone ever really "solved the mystery". After that, she just declined. Now, she is immobile(I would say that she is in a wheelchair but she doesnt get in that wheelchair, she stays in one spot in our living room and rarely moves because she can no longer do so with any sort of ease), in pain, depressed, constipated regularly, and always cold. We can't take her out to anywhere because she is always too cold. Plus, being in public makes her ansy and she gets mean and whines and doesnt enjoy herself at all.
So, she stays in our livingroom 24/7. She is immobile. She is unhappy and feels trapped and heartbroken. YET WE HAVE NO OBE AT ALL TO HELP TAKE CARE OF HER OR US. I go to school while my dad is home, my dad goes to work when I get off of school. We schedule our lives around the idea that she cant bealone because she needs constant care. This would be fine, except that the care she is getting fron us is not and has never been adequate. She doesnt take all of her pills regularly. She doesnt eat enough. She doesnt go to all of her doctors appointments. She is CONSTANTLY wincing because of either physical or emotional pain. We have no groceries. Our house is soo filthy. She rarely bathes. Her drivers lisence is two years due for renewal. The list goes on and on. And it's so WRONG. It's wrong and it's heartbreaking.
And in addition to all of that, my father is MEAN. He yells and critisizes everything she does. Physical abuse I know has been a part of it. So much happens when I'm not around. Sometimes my mom fabricates things and sometimes she is honest, I cant tell. For years, even before she was sick, my mom complained of abuse and felt trapped. She just never had anyone to help her leave and she didnt know how to do it on her own. Now, she cant. There are many reasons, or excuses, as to why I havent reported or done anything. Firstly, is my own fear and youth. I don't want to break up my home by calling cps or aps. I don't want to have to handle this and accept that my dad isnt going to. I'm young. I don't know what to do. A twelve year old doesnt know how to handle abuse complaints from their wheelchair-bound mother. The next reason is that my dad isn't a "bad man". My dad is just overwhelmed. He has never been able to accept help, but we need it now. He can't get anything done. I can't get anything done. There is so much pain weighing down on my house that I think we've given up. We're trying to function normally, but we can't just make small adjustments in our lives and pretend like it's working. It isn't!
I've approached my dad, but we both end up yelling and brushing it off. Which leads me to my third, and what my dad claims to be the most important, reason: My mom smokes weed, she has since she had cancer when I was verrry young. It eases her pain. Times when she doesnt have it, she'll fully face the actual situation she's in and it is miserable for her and for us. I wish we could have some type of outside, trained assistance without that being an issue, but we can't. Don't judge my family. My parents and sweet, fun, loving people. Life has just beat them up, and they've given up trying to stop it. I've approached some family.. My sister is in her freshman year of college so she knows everything I'm going through. I guess we've just been raised so that we feel like doing something isn't worth it? I dont know, but I can't take it much longer. I cry every single day thinking of the pain my parents go through and how they numb themselves to pretend it's not their. My dilema is that I don't know if I should say that their decisions are theirs and when I go to college they will handle it how they choose to. Or if I should tell a councilor and get adult cps involved. Or if I should go to college locally and stay home to continue emotionally supporting my mother. I don't know what to do. Please, please give me any advice you have. I need an objective view of what's going on.