Well, honestly I doubt that your father will ever leave, he is so codependent and emeshed in her problem that he will probably stay till the end...no matter what. As the years go by, the more difficult it becomes to let go and the older one gets the more fearful they become
when it comes to change.
All you can do is to work on you, try to detach as much as possible. The book Codependent No More was very helpful to me. It really opened my eyes and set me on the path of recovery from enabling and codependency.
Take care of you...you cannot change them, it is their life to live and you have yours to live, each of you on your own terms.