So Galactus has 3 revenge tokens. Can I use Running Shot 3 times? Or Say Running Shot, then standard range attack then something else? Or must they all be completely different actions?

Galactus' Trait:

YOU SHALL NOT HARM MY MASTER: Whenever Galactus takes damage, place a Revenge token on this card. At the beginning of your turn, remove all Revenge tokens and give your Herald that many actions as free actions this turn.

Page 8 of the rulebook:

A character may not activate the same game effect twice in one turn with free actions, unless the game effect indicates otherwise.

So you can't use a free action to trigger Running Shot more than once.