Was the cancellation completed --- i.e., both parties signed? You said you are "keeping $1000 out of the $5000 earnest money." Did you already receive that? So technically, the contract was cancelled, right?
If so, and if they still want the property, may I suggest that they write a new offer since this is a separate and new transaction from the one that was just cancelled.
Perhaps this time around, you can specify certain conditions so that you won't have to go through the hassle of dealing with a wishy-washy buyer.
Also...if someone else is interested in the offer you may want to leverage that interest to get a better deal this time around.