Codependency Support Group
Codependency is defined as someone who exhibits too much, and often inappropriate, caring for another person's struggles. A codependent person may try to change, or feel shame about their most private thoughts and feelings if they conflict with the other person's struggles. If you are on a journey towards self-love, this support group is for you. Join us and find others...

The flip side to this is what if you started behaving towards him like they do. See if his demeanor or attitudes change towards you. When he confronts you about it, Tell him "I was just treating you like they are to prove a point". Aside from this he has to choose. It's tough I know.
I guess you can be proactive like DaSquirm mentions and ask questions that will make him think about his actions, if so recite facts based on what you've seen happen in the past, maybe he'll make the connection
Gotta let him go, and get financially decimated, if that is going to happen.