The Saga of the Headers continued--I realized in bed last night that I hadn't taken CreateSpace's crop recommendations into consideration, and then I realized that because I was using actual layout software this time, I actually had many potential solutions! Of course, more way to fix things more precisely is a bit of a two-edged sword if you have a perfectionist streak, but I wound up reworking the headers so that instead of just moving them around, I replaced them entirely--which actually is less trouble, so yay. Of course, I once again failed to account for the shift from one-digit to two-digit numbers, but I fixed that and put a big note on the part of the layout that hasn't been proofread yet to pay attention to the transition to three digits.
Puff-pant!
Then I input the changes up through Chapter 9, which was the last of the proofed chapters. I think I will go dig now (couldn't yesterday), and tomorrow I will continue to proofread and input the corrections.