"My program will soon be used in most of the shops I go to for my daily bread."

That is very, very cool. I have made dozens of websites and programs, but I have never gotten to use any of them. Perhaps that is for the best in my case as poorly coded systems frusterate me (especially the self-checkout lines at grocery stores).

"But more than busy I've been completely stressed out. The limits of my technical abilities have shown in these efforts."

You are a brilliant and adaptable man, with years of experience in the IT arena. I have no doubt you can handle any new challange and the project will be a success. Also don't worry about not having the IT background. After STJ, I took some computer classes and it was really nothing eath shattering. The stuff you are working on sounds very cool.