This really hurts, doesn’t it. All you really want is for your family to get along and to be able to love each other. It sounds to me like maybe your parents are so overwhelmed by their own troubles, and maybe by parenting 5 kids, that they have stopped even trying to make things right. What really needs to happen here is some family counseling. No family can function well if the two parents aren’t even speaking to each other.
It’s at least worth a try to see if they would agree to take the family to see a counselor. If you make the suggestion when you’re angry, they won’t hear it. Approach them when things are at least relatively calm and tell them how worried you are and how much you want your family to be better. Then give them the phone numbers for your local community mental health center. Fortunately, you live in a city where there are several. (I’d give you a phone number but I don’t know specifically where you live. If you do a web search by entering your city’s name and counseling services at least 8 different centers will come up.) If your folks don’t go, at least you’ll know you gave it a try.
Whether the family goes to therapy or not, you still need to take care of yourself. You’re a top student. In less than 2 short years, you’ll be able to go off to school. You need to keep your grades up and do well on your SATs so you qualify for scholarships. Personally, I think the SAT classes that a lot of schools run are a really good thing. They help you get used to the test and give you practice. You also need to develop yourself through sports or arts or school clubs or volunteer jobs. Colleges look for people who are active and who have found ways to learn skills in teamwork and leadership.
It’s okay to look for other role models. That doesn’t mean to stop loving your family. Just don’t expect so much from them if they haven’t got it to give. A healthy choice is to find other people who can give you caring support, who can listen to your troubles, and who can give you good advice. Teachers, youth leaders, clergy, counselors, and often the parents of good friends are candidates for the job. Find some positive people and make time for them. Do remember that relationships go two ways and that part of making an alternative “family” work is to give as well as to receive.
I wish you well.