Gin, I can empathize with you. Been through that a time or two myself. Unless they are familgy members it's time for them to go! And even if they are family members, if they cannot respect the rules of your house, then out they go. I would never have given them a car, because if they get in an accident, even with insurance, unless that person is listed on your policy, they are not covered and you are liable for any damages and/or injuries.
Surely there are agencies that can provide some form of assistance to them somewhere in the state. If they cannot properly look after their own dog, then the dog needs to be rehomed.
Don't be a doormat for them, regardless of the circumstances they are in. Like my mother always said, company like fish, begin to smell after three days.
You are in my prayers, and I hope for a quick resolution to your situation.