Paint shop jail... No parole!!!
Now that I have been screwed more than once with life lessons like this. I don't prepay for work, doesn't matter if it's the gardener, painter, or whatever. I will do reasonable deposits and progress payments. I don't really care what they tell me I make decision on what I see. The key here is "actions speak louder than words".
Sounds to me only based on what you're saying. That it's time to cut your losses and pick up the car and move on. Maybe small claims court if you have a written contract and proof of payments.
Good luck!