This would be a massive waste of your time.
Not only would it be an admission of guilt, but no company is going to let you pass stealing from them because you wrote a letter.
Not going to happen.
They WANT you to suffer... and to tell all your friends how you suffered.
That is why they hit you with both the charges and the civil demand. I know you haven't thought about the civil demand because you haven't mentioned it.
This is a civil fine above and beyond anything that happens in criminal court and can and will run several hundred dollars.

