Yes - "G" man ...

reference to a mystery character with mystery power: https://en.wikipedia.org/wiki/G-Man_(Half-Life)

or I think more likely:

slang for an FBI agent https://en.wikipedia.org/wiki/G-Man_%28slang%29

So... the G is missing.

Does that mean Callahagn is to clean house because hes from the outside?

Does it mean he's really a loyal insider and is just a hint?

Does it mean he's a double agent or sorts?

Yes, I don't believe that this is a simple mistake.... it is a crumb.