The fact he showed up unannounced is a big red flag that there is some tomfoolery going on. He wants the game + the money in the end. It's a done deal, he needs to move on with his life and stop acting like a f***ing manchild. If I was the buyer, he can sit around with the uncashed check for all I care.

Exactly. There wouldn't be any trust left. No matter where things were left off in the communication chain, it's over at that point. I would send a communication back that we are done here and request no further communication and any such attempts would be ignored.