Greetings,
Truth is NON-negotiable. His work either exceeds the customers specifications or you bust his act wide open. Your job is nearly 99% documentation so I don't think we need to discuss how you do it, but you owe it to yourself and all the others behind you to be honest and break the hacker down. Don't ever regret suffering for what is right...if that happens then it was time to go, whether you are ready to or not. You only have one choice. You go to work and do the job you agreed to do or you are no different the the 'turd' you are talking about.
Where there is no alternative...
There is no problem!!!
Later Bro', Petergunn