All in all, I'm pretty confident the merge will work. Well, except for one or two chapters.
The main one in question is Chapter 46 and, as I reached that piece, it left me with a little "Do I need this here?" niggling in the back of my mind. Basically, it imparts knowledge about the state of a certain person as they learn about said state. But that knowledge is taken in via a third party, whereas the next chapter has, in my mind, a little more of an oomph as it's the same knowledge being taken in from the PoV of a character that has stronger stake in it.
Now I like several things about the chapter and it gives a certain insight into how other characters see the MC. But that can be readily dragged into the next book if needed that much.
There's another chapter, #52, that's not as problematic, but, what with everything surrounding it, may be superfluous. I've had all of it--the places, the characters and their timelines--in my head for so long that everything is already one and, even if I wind up removing both chapters, it's still roughly 20,000 extra words.
I guess it's time to go hunting for a second opinion...