It sounds like you still have a lot of you invested in that restaurant and those people. I don't know why you quit/"moved on" and yet still go in there so often. If I had a bank account that registers only $12.29, I would not be spending $200/month eating out (especially in only one place).

I don't see what issue you think the GM can solve; you had a bill you could not pay, for whatever reason. The "how much" issue is a your bank and you issue and you imposed it on the restaurant, where it does not belongs and want to worry about who said unkind things to you (who cares, you don't work there anymore!) when you were having financial difficulties and causing a problem for others.

If you don't like what people say to you, how you are treated, do not associate with those people! Get your money management in order so you do not have to be embarrassed again (keep a spare $20 in your wallet?) and leave those people to themselves and their attitudes. If they treat other customers like that they will lose customers. Nothing said to you was "wrong", just perhaps unpleasant/unkind/not something you think you would have said if you had been in that person's shoes. Technically they could have had you arrested?