"We want Falmer" makes it pretty clear that we would never have left Withdean - the club could not raise the money due to the credit crunch. Who knows what would have happened.
You tinker!
No, neither do I, but it would be good to know what contingencies are in place for when he passes away, for example.
Edit. I do remember reading in "We want Falmer", that the money for the build of the stadium was ringfenced just in case he was run over by a bus - no-one other than the club...
On this point, as El Pres and others have said, I don't think he wants or is expecting to be paid back. The importance of getting to the Premier League is that it means that the club will be able to run without him having to fork out every year (if it still runs at a loss, we really are a bit...
To answer the rest though, my understanding is that this is an interest free loan that will be converted to shares if the club does not pay it back in about 20 years time (or 20 years from when the Amex opened). As TB is still putting money into the club, we do not even know how much the club...