I'm sure the Doctor would have blown up the TARDIS if necessary...but I guessed from the first that the "self destruct" was a piece of food.
It's really a mark of how much he's become "better" that he was originally willing to blow up Gallifrey to destroy the Daleks...but couldn't do it again (with Earth).
The bit with the TARDIS key was great.
And, I'm finishing this post several days later, so I have no idea what I was planning on saying after that. Sorry.
Another crack in time!