Nice writeup. It prompted me to checkout Wikipedia about Pai Mei, since the story about him killing those Monks in 1003 would have made him a thousand years old---something that seemed a little too fanciful for _Kill Bill_, since this film seems generally to eschew supernaturalism of that magnitude.
Turns out, according to Wikipedia, that David Carridine flubbed the line, and that he was supposed to say that Pai Mei took his vengeance in
1883. In my mind I'd sort of worked out that the Pai Mei of the film was perhaps the most recent of a series of persons who'd carried that name and most of his characteristics (something like the way the actors portraying him have done), including the Pai Mei of 1003 who was such bad news for those monks.
I think I prefer my rationalization of Bill's story to the one contained in the original script.