I'm a longtime user of Google App Engine / Cloud Datastore / Firestore and wrote a Java ORM for that environment that has achieved some popularity. I really like the datastore for some applications, but there's a pretty good chance that it's a bad fit for you. While I'm only casually familiar with your problem domain, it seems at first glance like the kind of thing that would scale reasonably well in a traditional RDBMS. You could would get a lot of value from joins and aggregations, and you don't really have zillions of elements changing all at once.

I could probably give you some advice on how to use the datastore better (most of which would be along the lines of "don't denormalize, store foreign keys and use batch key fetches instead") but it might just be the wrong tool for the job. If you want to talk about it, contact info is on my profile.