Hi, it sounds like he's setting you up to having to force the issue. From his POV doing nothing is the same as positive action because you can't physically force him out. All he has to do is dig in, and that would be in line with his past behaviour which is based on NOT doing stuff, like paying support or working.
Your best bet for now would be to plan for him staying put. Are you able to get your name off the lease? Have any mutual debts, or bank accounts he can get to? any valuables he can get his hands on?
Possibly he'll stay where he's comfortable and provided for, so think about not having any food in the fridge, eating out with your son, and letting him fend for himself as much as possible.