there was any chance there might be a back door
Why the NSA Called Me After Midnight and Requested My Source Code
Peter Avritch

Fascinating story and you have great storytelling skills, really enjoyed reading this! My issue is that your are selling an encryption product, and most people will trust that there is no back door and that their data is secured, but in this scenario, you were the back door. Did you put a disclaimer afterwards mentioning that the US government had the source code and could crack even the paid version? There is a massive trust issue here.