SQL Server's OpenJson function will let you dismantle JSON structures into relational tables, including tables with foreign/primary key relationships.

I'm adding a table and subclass table to my DB. (Subclass table = table where the primary key joins to the primary key of another table, to give extra row information to some subset of the rows ...

When working on a multidimensional design, every fact table within scope should be handled with care. In an ideal world, each low-level fact table represents the metrics related to a business event.