Tobi was parading around as Madara. If Madara has survived the fight with Hashirama, even though he was supposed to have been killed, having a disfigured face would easily be explainable. And he called him Mizukage because Tobi was the real Mizukage, as he was controlling Kagura.
And the Rinnengan thing? Nagato has FAR too much control of his Rinnengan for it to be a transplant. Tobi was just being an arrogant douche monkey like the real Madara and Sasuke have been shown to be. And as he was shown to be before Minato beat his *** like a naughty child.
Tobi was only about the same height as Minato when Minato was crouched into a fighting stance.