Opinions please

Get rid of it like a hot potato. Guy is obviously ready to start ****. What if you keep it, build it and then he comes back and tries again legal or otherwise?...Even if he doesn't succeed, not worth the :bs_flag:over what might be scrap metal.
As for the $. He did agree to pay. Ask him what he thought it was going to cost. Get as much as he will agree to and tell him to pick it up.
AND I would give a receipt detailing what you did. Note need for further cleaning/checking needed by machine shop to check for damage. Show Full price and hours, previously agreed price, adjusted hours and final accepted discount price. Have him sign a copy noting picked up for your records.