I don't think it is unhealthy to think the way you would be glad to wish him dead.
I was talking to my brother yesterday about this same issue. Our mom passed away before her Psychopath like husband. I didn't organize a party when he died but if you had been in the room when I got the call you might have thought I just finished a call with a telephone sales person, no emotion, I was glad he was dead, I saw a side of myself I would never have imagined, a feeling of relief. He treated my brother and I like his slaves, I was stuck because I was caring for my mother and had to toe the line and deal with him for 5 years. His evil did get a rise out of me when I got the will in the mail and guess what he left what should have been for my brother, sister and I to his drug addict daughter who is married to an x convict. I never knew I could be so angry, I actually slammed my fist down on my laptop so hard I broke a letter. You wouldn't have known it was me I was on such a rampage. And yes then I was really glad he was dead. I don't believe in being in a state of hate and develop a list but I do have one person on that list and that is just how I feel. It is a tough feeling to deal with and admit to having. I am working hard to move past it.
Twin, if I were to wager a bet your brother is working your mother for everything he can squeeze out of her. I am very sorry that it had to be at the cost of the time with your mother.
I think there is a line between wishing someone was dead and having the strength to move beyond the hate. It is tough to even believe I would have such feelings.
Di