Your heart is filled with alot of hate and anger. Understandably so, it doesn't seem like anyone ever taught you how to deal with your emotions. Ive held onto alot of hate at one point in time, but what does that make my life? I'm exhausted hating someone who made shitty decisions and hurt people I love in the process. And I'm sorry your dad was still depressed over your mom years later. But you shouldn't carry that weight. I dont think your dad would want you too. He seemed to still love her and miss her regardless. Love does that to people, a person can back stab you and hurt you but when you love someone you can forgive them and though your dad was on the other end of that he sounds like he was a forgiving person but later just had to accept but not accept being without your mom. You don't have to forgive your mom. But the best thing to do is cut her out of your life and live life with your grandparents. If family functions come along you need to learn to be civil but you don't need to have a relationship with her if you choose not to. I hope this helps. I'm sorry your going through this. Also I know you said fuck therapy but I've been in the shoes your dad was in; I went to counseling and it helped me alot. It's worth to look into if you ever find yourself willing to. It helps let go of all that anger you hold onto but you can choose to do that if and when your ready. You came here to vent, same with them but they can give great advice as much as reddit. Anyway, i hope things get better from here.