You unfortunately have sold to "SCROTE M _____________" (fill in the last name)
I had a customer several years back we Nick named SCROTE M SORENSEN.

I wish i had the time to write all the details out but will try to summarize.
1st. there was a dash knob missing. I said Ok send me a pic of the panel (Vintage air) and I'll order a replacement.
2nd 2weeks later, A rattle when it IDLES. OK send me the pic, I'll get the knob, install it and fix the rattle.
3rd. 2 more weeks, There's scratches on the ignition switch cover, was this a used part? NO
4th 2 more weeks, I suspect all of the work you did you used parts. i want the make model and VIN # of the cars you took the parts from.
This went on for over 6 months with many offers by myself to address the IMAGINARY issues. After 6 months i told him i was done and rescinded all previous offers

3 or 4 months later I was served with a notice i was being sued.
get an attorney involved XXX $
In spite of the fact that everything was done in writing it had no bearing on the current situation. My attorney advised to settle if possible as the court and his fees would likely exceed the amount involved.
After several more months and more lawyer fees A settlement was finally agreed to. Total cost about 5K on a 9k invoice Fortunately the lawyer was a friend.

IMO: You have made a transaction with SCROTE
your choices at this point
1. Try to reach an agreeable cash settlement.
2. OFFER buy the car back offering to split the transportation costs
3. Contact an attorney
I did not read this entire post but if you have anything that states the vehicle was being sold AS-IS it would be very beneficial. IF not see 1, 2 or 3 as I do not think this guy is going away SORRY

BTW: he pulled the same cr-p on his attorney when it came time to pay the bill. He claimed he didn't get the representation he was being billed for. In my case it was he didn't get the QUALITY he paid for