First of all, everyone is correct on the legalities, but you don't have enough damages to pull a lawyer away from a sushi bar. Obviously, this should never get to court, but if it does, it should be small claims court and you can easily represent yourself. You have plenty of evidence, so make sure you print all those messages.

Post the guy up if he doesn't respond to an ultimatum. You don't want someone else on the board to get screwed if he has more shit for sale.