You seem kind and thoughtful to care about others. While those are good things, evil people (like restaurant owner) will see it and mark you as spineless, then try and take advantage of you. Remember, Jesus was murdered.

Next time just tell the bartender there’s no tip being charged, she can simply keep the food and cancel the order if it’s going to be an issue. The bartender is only a peripheral character, the owner created her behavior and encourages to continue. She’d change her ways or be unemployed if this were any other business.

I sincerely recommend if you ever have the displeasure of setting foot in that shop again, that you tell the owner to his face, this is his opportunity to suck your cock.

I’m not saying you need to ditch your integrity and kind deeds, but getting comfortable with being rude and confrontational in person, prevents your story from happening again.