Got a trick for pacing and removing unneccesary stuff.
For each scene, chapter, arc, etc.... you gotta ask yourself this:
1-is this relevant?
2-is this entertaining?
If the answer to both of the questions is no, remove it.
If it's relevant but not entertaining, you got an info-dump. Figure a way to share the relevant information in a more entertaining way.
If it is entertaining but not relevant, you got filler. Filler is okay in moderation, but in your case it sounds like you may need to remove a lot if you want to shrink the scope of your story.
If it is entertaining and relevant, keep it. That's the good stuff.