I'm not sure if this is a good idea or not. I just found out that if you hire a PI and they find anything illegal they have to turn it into the cops... e.i. the pot (I found this out because my AH does pot). He could then go to jail. I didn't follow through with the PI because I didn't want to open that can of worms. But if he goes to jail or is caught with pot you could get a PFA so he couldn't come back to the house.
I know it's out there... Just a thought... I was also told when my husband wouldn't leave that you can't force someone to leave the home until after the divorce. Now you said you got the house in the settlement. If it IS settled and you have paperwork. I think you can have him removed. You may have to serve him papers first.