Adventures of a rookie writer

These days I can't shake off a certain quote from Sherrilyn Kenyon from my mind: "The most difficult thing for a rookie author is to finish their book" (not exactly the same words). I do remember Forbidden was hard to finish, but it had cooked in its juices far more than Forbidden: New Days.
This book is giving me a bit of a head trip. I am 95% done, and the 85 to 95% part was more difficult than the 0 to 85%. Now comes the delightful last 5%, where I will find... ta-daaaaaa...
- Blank spaces I am supposed to fill... somehow.
-Parts that put a plot hole I need to fill... somehow.
-Removing those parts will give another, bigger plot hole.
-Parts I simply liked and make no sense. These can be saved for another book! ...perhaps.

I wonder if going from rookie to pro involves becoming formulaic, which seems to be the solution for most writers. Please, I want you to give me a great, stinging slap if that ever happens to me. I'd hate being formulaic! Surely there has to be a better way.

Maybe in a couple years I'll be able to tell...!