The novel had a doctored recording of the assassination attempt and he might've shown it before Padme showed up.
Audio recording of the Jedi showing up. Palpatine messured his words until after killing the first two or three Jedi quickly, then yelled for help, jumped back and put his lightsaber through the recording device. Then proceeded to fight Mace like a Sith Lord.
That's entirely possible, but like the novel of Star Trek V giving an explanation of how the Enterprise made it to the center of the galaxy in a few days, if it wasn't in the movie, it doesn't count.
You act as if those are mutually exclusive. Except when you do. The way they interact in the opening act of ROTS, for example, is equal to TCW in this respect. Not sloppy writing, a deliberate change. How do you think the original concept would have played out on screen? What do you think people would have said about it? Just how "great" would this scene have been, though? It's not like Anakin would have just handed over his lightsaber to Obi-Wan at some point, not being done with it and all - so what we're really talking about here is a scene where Anakin says to Obi-Wan, pretty much out of context, "In the event that I die before you do - snicker - I want my kid to have this." It would exist only to tick off a box, like the "3PO must be memory-wiped" scene.
Well either he knows when to keep his "mouth" shut...or his swearing filter keeps anyone form knowing when he's not telling a tall tale.
Probably a little of both, I think. R2 knows he'll be disregarded by Threepio ("Yeah, he thinks he's awesome. I am better than that stuffy protocol droid...") and that most humans don't understand him. So he can keep whistling Dixie...