Thanks for doing so much work figuring out the order of constraints. I looked last week and could not find Microsoft documentation on it.

The problem is bigger. Triggers play into this mess. I have "Instead Of" and "After" triggers and trigger ordering on a single table in many cases. This firing order mess is also mostly undocumented. The "Instead Of" will fire the "After" triggers if you do a DML statement for that table inside of the "Instead Of" trigger. But, my questions ran deeper, wondering if some constraints ran before or after triggers. What rows are in "inserted" and "deleted" for each trigger?