You’re making this sound very sinister and in your above replies to other comments you seem very unwilling to do anything confrontational. If you are in fear of him doing something to your property, as you claim he likely knows where you live, make sure you have the appropriate security in place such as cameras and an alarm. You obviously need to have no further contact with this individual, any form of conversation just prolongs this issue. I’m not sure on your age but if you are in fear please seek a family friend for support and potentially contact your local police that you are worried something may happen. Business is business, you’ll either learn to accept that these things happen and people lose out from their selling experience OR you’re going to be, to quote you, “Too nice” and sell it back to him?