Here is an update. I have consulted with two local law firms that specialize in real estate.
This is first version of the "no sell" clause that I have in my contract, and it is very, very weak. Later versions, and there are several are much more defined, restrictive and enforceable.
Both attorneys believe that the developer would have a hard time proving his case in arbitration. The contract requires arbitration, so it wouldn't go to court. Of course there are no guarantees!!
They both believe that I have the right to sell the property since I entered the agreement in "good faith" and with "intent" to occupy.
The developer has sent out written notices via their attorneys to sellers with this first version, but to their knowledge not pursued it any further.
However, the developer has pursued later versions and won in arbitration.
Their advice was to sell it with low level marketing (no sign in the yard etc) and ignore any initial letters from the developer unless they are actually pursuing arbitration.
They believe the For Sale sign in the yard will be the main point of contention with the developer. Hopefully, without the sign nothing will come of all this.
Wish me luck!!