Do I really have a reason to be afraid of going to jail over this? Or did I really do something wrong here?

You certainly live an interesting life. I would threaten to countersue if anything develops from this, which I doubt it will. You really should write a detailed letter to the headquarters of Subway, repeating part of what you describe above, and detailing your humiliating behavior at the hands of their franchise. Be polite and accurate and let them know your true feelings on this. Maybe a talk to a local TV station that does public affairs/consumer stories would be in order. You were mistreated by a psycho. Check the links.