lol ginko very well said:P
i would do as ginko said, give the money back if you can as lets face it, there are loads of nice buyers out the who would be understanding and if he is being an idiot as you have said would you really want him to be a regular??
as to bad feedback, if you say it how it is in any sort of response then i dont think you have anything to worry about he will just make himself sound un-reasonable for not accepting that technical clitches do happen! what else could you have done??? …..it sounds like you have kept him in the loop AND offered a different option so i dont think that you have anything to worry about:)
sam xxx