I'm reasonable sure about my answers, but I could be mistaken on some of them.
If a player performs multiple heroic actions simultaneously, does that player get multiple Fame tokens? For example, let's say there are three Minions in Monarch City. If I attack and slay all three of them, would I get a Minor Fame token for having attacked Minions in Monarch City and one Major Fame token for having slain two Minions in a single round of combat?
You would get tokens for all actions.
Does attempting a heroic action stack with succeeding at that heroic action?
What about multiple failed attempts? It seems weird to me that a player could potentially get multiple Minor Fame tokens for failing to slay three Minions in a location while the player who slays them all on the first attempt would only get one Major Fame token.
My guess is that fame tokens in this case is supposed to be limited to once for that combat which should normally be once a turn. But you could reason that if you attack 3 minions and fail to kill them, walk away from the minions and then decide to attack them again all in the same turn, it should be counted as 2 separate combats and therefore award 2 minor tokens.
To clarify, "Slay 2 or More Minions in a Single Round of Combat" means that an actual combat action must be taken against the Minions, correct? So, I am correct in thinking the Shaman's Arrows of Destruction ability would not qualify?
It would qualify since the minions were slain by the Shaman. Playing special cards that removes minions, like cavalry sweep would not qualify. The minions were then slain by the cavalry and not the Shaman.