I know Kripke said he had a five year plan, but he also said there was no such thing as angels. So, I think that all of season five was a fly-by-the-seat-of-his-pants type ordeal that's the only way I can explain away the pacing issues.

My theory is that Chuck and Becky are actually still together on a Caribbean cruise. God just wanted in on the very end and has a flair for dramatic narrating so he beamed into Chuck's house and typed up the last chapter of the book.