A little question about Balon. I'm assuming that if I bump his strength up with a card, say Iron Fleet Scout, that also increases the minimum strength a character has to have in order compete against Balon in a challenge?

That's correct.

That should be the case, as otherwise "printed STR" would have been used instead of just "STR". It's surprisingly difficult to find a reference to this in the rules though, as the entry for "Strength, Strength Modifiers" in the RRG focuses on determining Total STR for the challenge.

Under "Modifiers" it's implied that the modified value *is* the value for all intents and purposes. On one hand it could be slightly clearer, but on the other hand I'm at a loss to how without going all Tautology Club on it.

It's not implied in the entry for "Modifiers" (RRG p. 13); It's stated outright:

"The game state constantly checks and (if necessary) updates the count of any variable quantity that is being modified."

So the value of STR, the count of a variable quantity, is constantly checked and updated. And since it is Balon's STR at the time the challenge resolves that matters, modifiers to Balon's STR count, no matter when they are applied.

Right. I don't know how that could be clearer without getting into something so pedantic as to say "Modified STR counts as STR for all card abilities." It's in the category of "really? Does this need to be spelled out at a third grade level?"

The only way you could be confused about it is if you weren't exactly familiar with the convention of using "Printed [_____]" as the exception, and had the mistaken impression that references always referred to printed, and expecting cards to specify "Modified [______]." With new players coming into the game, I'm just trying to be mindful of what we take for granted.

Thanks for pointing out the reference. 

Right. I don't know how that could be clearer without getting into something so pedantic as to say "Modified STR counts as STR for all card abilities." It's in the category of "really? Does this need to be spelled out at a third grade level?"
 
The only way you could be confused about it is if you weren't exactly familiar with the convention of using "Printed [_____]" as the exception, and had the mistaken impression that references always referred to printed, and expecting cards to specify "Modified [______]." With new players coming into the game, I'm just trying to be mindful of what we take for granted.

No, because the conversation started off with somebody being confused about the rules as written, and the fact that it was more pedantic than the written rules was the actual point being made.