My mom annoys me now?

You know despite everything that you know about your father, she may have actually loved him. Even if love was not part of the equation, she was dependent upon him and thought she was better off with him than without. I think her need to tell you the gruesome details of their union was probably an effort to have her children love her, because plainly her husband did not. That is pitiful and sad. However, It is the way it is. You are probably mourning the storybook family that you wish you had and never got. I doubt that you were fine 2 years ago. You just buried it and the knowledge that he is finally going and there will be no redemption is depressing. Who wouldn't be depressed about that. The unfortunate truth is that your mother was weak and you will have to learn how to set boundaries and choose better than your mother did.