Hi there,
I don’t have much in the way of advice for you here but my heart goes out to you as I know how you feel. It’s very difficult coping with a partners addictions, I’m there in that very same struggle myself right now so I can relate to the emotional roller-coaster it causes. Regarding your car, I would say quite right that he shouldn’t be using it, it’s not fair on you should anything happen so it’s reasonable to protect yourself that way.
I hope your situation gets a bit better, look after yourself ♥