You sure painted the picture of your family's dysfunction in a very fair way. I commend you for seeing both the good and bad in everyone. I think you have good insight into much of what is going on.

Your father is both enabling his family's bad behavior and the cause of his family's anxiety.

You are not responsible for your family's behavior--only yours! You probably learned to be passive because if you get to confrontational--you could get thrown out! Though you have to establish boundaries between you and other family members--because of their issues, I think you intuitively know their is not much you can do. At your age, where you need to invest your time is into becoming independent and eventually financially secure. It is important to try to disconnect and develop a plan to get yourself in a situation where you can leave. I am an Air Force veteran--serving in the military was one of the best decisions I ever made--something to consider.

Whatever you do, try not to negotiate the relationship between your mom and dad, dad and sister, etc. that is not your responsibility at this time. You are in a tough situation but need to try to figure out how to accept it and let go. We cannot change other people--only they can. You sound worried and caring but sometimes that is not enough; hopefully, they will eventually see their situation more clearly. Hugs.