The Length Question

I might finish the book today. I have about a chapter and a half to go. I know what happens in the rest of the chapter, but I'm not really sure about the last chapter/big finish. This wasn't supposed to be this big a rewrite. My agent thought it would require just a few little tweaks. But the questions she raised sparked ideas, and then those ideas led to a few little tweaks -- but then those tweaks has this massive domino effect that changed more and more until I pretty much had to throw out...