I wish you well with resolving this. Most of us here would gladly make the trip to Texas to make our feelings known to this miscreant in person.
As a retired LEO I can tell you first hand that the old adage "The squeaky wheel gets the grease" should be your guide.Dealing with any agency from afar is difficult with lack of interest due to the case not having a local victim to answer to.The standard response when a request for assistance is made is that the case is a civil matter rather than criminal.From the many replies it does appear that the various victims including you, did indeed enter into a civil contract involving an agreed trade of goods.The criminal aspect is that the goods were misrepresented involving fraud/theft. Remembering that squeaky wheel you need to burn up the phones to any and all the agencys in that area and don`t be satisfied until you speak with the Chief or Sheriff directly. From the documentation from your incident and the others from different forums it would appear that this miscreant is operating a continuing criminal enterprise. With the facts you have and others that I`m sure will come to light it may be that you can gain the ear of a state attorney or other and have this clown prosecuted under the Rico statute.It is apparent that this isn`t an isolated incident and that he has no intention of quiting.
Joe


"......ain't many troubles that a man cain't fix
With seven hundred dollars and a thirty ought six."