I've heard the phrase "passt schon" used to mean:
- Never mind: „Ich denke... nee, passt schon.“
- No problem: „Entschuldigung!“ „Passt schon.“
- OK: „Wie geht's?“ „Passt schon.“
What can it mean in Bavaria? Is there a good English translation?
I don't think you could translate it with an English word 1:1.
As you said yourself, it can have many meanings in German. In fact, you can say it in response to almost any question.
Generally, it's used to make something less important/worse/interesting or to express that the other person shouldn't worry about something.
There are many translations for each of these situations, so I think you should translate it how it fits the situation.
"It's all right" may be the best for most situations, but certainly not for all of them. As this is very, very, very informal you should translate it as it best fits in the situation. There is definitely no "universal" translation for it!
"It's alright" would probably be the closest translation, but as you have shown, other words are more appropriate in many situations.
The translations you show are the best ones I think -
"no problem" when used as a response to an apology you don't feel is necessary
"never mind" when used to "undo" a previous sentence
"you're welcome" when used as a response to a "thank you".
This is highly informal language - there are many situations where it might not be 100% appropriate.
Another meaning:
Paying your restaurant bill and saying "Passt schon." means "Keep the change.".
There's also a more sarcastic/ironic version, "Passt schon" or "Schon recht" which could be translated to "whatever [you say]" or "Yeah, right". The meaning of it is very close to "Bullshit", but packed into a more polite "It's wrong and you're wrong and I tell you that, but if you want to believe it then so be it, I won't argue with you".
Example:
A: Wusstest du schon das...?
B: Nein, das glaub ich dir nicht.
A: Doch! Das ist wirklich so!
B: Passt schon/Schon recht.
A: Did you know that...?
B: No, I don't think so.
A: Really! It's true!
B: Whatever.
I don't know how widespread that usage is, I at least know it to be used in Austria.