You don't need to grill him about it or understand his motivation. He has been pretty clear about it. Accept it.
What are you comfortable with given that fact? If you need to have him move out, have him move out. If you are going to tolerate it, tolerate it. Control yourself, not him. Figure out your own boundary, and enforce it.
Quit going to him to try to get him to fix it. He won't. The arrangement is working for him.
