Do not respond to him in any way shape or form from here on out. Have your attorney send him a letter. The worst thing you can do is get this guy posting bad reviews about you allover the internet.
Setup google alerts for your name and company name and respond to anything he posts about you with the full story and leave out any emotion. Just the facts.
People who read reviews will figure him out pretty quick.
Avid Stamp Collector - I really love 39 Cent Stamps