Sorry but Citizenship application is probally the least complicated application and that guy was able to waite your 2 years when you had  more than pleanty of clues to be certain he was misusing the money order. You could've have found out who cashed that money order like 2 years ago and reported that guy to the police. jesus..bihana bihana rannnaaakaa reesss oothyao .. how can a grown up man with green card and who can read/write English be cheated like this? 
now don't be a gentleman again and forive that bastard or he will be waisting and causing big pain to other families and they may not be lucky as you because at least you already have your green card. all you have to do is place an inquiry where the original money order went , and if misused , report that guy to police or at least make his name public so others will be aware of .