Not fixable?

I'm about 3/4ths the way into changing NEARLY HUMAN from 1st person to 3rd person.  I'm really having trouble gauging when to use names or pronouns or some other identifiers.  I'm committed now, I've made so many changes to the manuscript.  I'm doing my best to make it read O.K. but I think I'll have to copy-edit a whole bunch of times until I get it right.  For instance, I can take out pronouns altogether sometimes simply be reorganizing the sentence.

Writing is complicated.

Anyway, at this point in the story it's mostly action narrative -- but some of it is pretty silly.

Problem is, it can't be changed.  No way to change it without throwing the entire second half of the book out. 

This is the consequence of forcing the book, I think.  At the time I had a less serious, more satiric take on the story, so using PETA people as his assault forces, and making comments about rampant growth in destination resorts, and things like that weren't so out of place.

Basically I have an out and out gun battle with zombies -- who I call Shamblers -- using a bunch of outraged PETA members as the army.  (The Old Gods have been taking their pets and eating them.)

A cute idea when it isn't serious.  Silly, when you do it seriously.

I'm afraid at this point, it probably just isn't fixable.  I'll just have to hope that if the reader has made it this far, they'll give the story the benefit of the doubt.