I'm going to joke about my ex's dead dad's name
Why would you joke about your ex's dead father?
I'm a mean person and I know how much the thought of such a joke could hurt a person
Leave your ex alone, no wonder you're an ex because you are heartless and spiteful. You should always respect the dead and never joke about them especially if the person was close to them. Just leave your ex alone and move onto another relationship.
I'm dead inside and have no empathy. I just don't care.
I'm sorry you feel that way, but it's still no excuse to joke about anyone's dead parent.