Is he in Colorado? Has anyone tried calling the State District Attorney and tried to file a complaint? In Colorado they arrested Mark "Shifty" Shifter who was running a raffle scam and taking peoples money without having the raffle. You may try that first and proceed with that before spending money on layers and investigators and see where it goes.
You can try, but there is a difference between civil and criminal law. Generally speaking, an attorney general or district attorney usually is very reluctant to turn civil disputes into a criminal dispute. You would not want the police to arrest you if you missed a credit card payment, would you?
Look into a civil action. Once you file a lawsuit, you can start discovery. If you have a suit going, it might be possible to subpoena bank statements and financial documents from banks and other third party institutions. That's a good way to start figuring out what someone has.
I'd start looking at aggressive lawyers/firms that collect bad debt. This is sort of like that. Most of them have PIs and others they work closely with to recover bad debt. They will have a good idea on how to proceed with something like this.