Welcome back to the roleplay, Veoline.

Regarding the precise timekeeping system, I think that it could work. Perhaps it could also be helped if each part is explained which time period (group of pages) a part refers to. For example:

Era of pages 21-25: blah
Era of pages 26-30: blah

I think as it could be anywhere in those 100 years, side stories only affecting one's own race could take place in different parts as well as long as they can be reasonably timed. If one story ends up in a city destruction, but the player wants to continue a side story that needs the city intact, it could be said to have happened earlier before the city was destroyed.

What does everyone else think?