[Rhod the Red]

"he was apparently granted more power and authority" What makes you say that?

"Gandalf, in his sent back state, was the "caretaker" of Middle-Earth at the time." No he wasn't, the Istari aren't meant to govern Middle-earth, but influence their inhabbitants to resist Sauron.

"he was the steward of the steward" I think you're taking his statement literally, Gandalf was merely speaking in the context of having responsibility for others, to Denethor.