TBH, that sounds like a *LOT* to digest in a single narrative. I had a similar issue with mine.
Essentially, my *main* story is about the group of people escaping the planet (this one). What I had started to do was to try to write the backstory (as mega-flashbacks) to each ofthe characters of the group (over a hundred characters on this voyage). This is where confusion would reign. I’d talk about a particular person in the past tense (ie dead), but in the next chapter, that person would be alive given the flashback nature. (Even had a review that stated this issue… they were confused.) Thus, I split the stories off, and it was a GREAT decision even though I’ve yet to make any progress that main story.
For instance, Alaska Trekkers was the first spin off, focused on two. To be fair, it almost reads like two stories by itself, the very strong “inciting incident” that sets up the conditions for the second part, the evolving social conditions which effectively pushed the two characters into joining the main quest. It’s now a 206kword story. From this story, I was able to create a halloween oneshot (The Phone) and a holiday oneshot (The Phone, Part II).
Then, I was working on the backstory to the main protagonist of the main story, simply the evolving childhood of him and his friends, turning it into an episodic serialization. However, I realized I needed a swimming instructor for him, which led to Jefferey.
YES, it’s a rabbit hole filled with plot bunnies. However, TBH, it’s quite fun and lets me explore aspects of this society the main group of people are fleeing, and why these characters are being persecuted, pressured into taking what could almost be described as a suicide pact (not their intent, because they’ll turn it into a chance to survive/thrive).
Overall, I think this does better justice to each character. In the main story, might have some mention to their backstory, but I won’t have to go into three chapters of detail. (And it does create some interesting cross-overs between the backstories too.)
My suggestion is that you do the same, peeling the flashbacks & backstory off into separate tales. Lets you focus each one onto a specific character. If a reader on the main story is curious about character X, they know where they can turn for the detailed backstory.
BTW – the above is a suggestion, nothing more. Advice to avoid having a million word monster intimidating the reader away.