I think it might accomplish more to wait a few days or hours for them to do something that egregiously violates community standards, then defederate en masse—and use the defederation as an event to draw media attention to their practices.

I would make a simpler and more objective rule: no instance should host more than (say) 25% of active user accounts.

Offer courses in community moderation using the university’s instance?

I wonder if the first days of SMTP were like this—people sending emails to each other in amazement that messages could reach people on other servers.