I personally think your idea of requiring your FB group members to follow you is a terrible one. Very selfish, and not entirely community minded at the end of the day. Requiring some kind of vetting makes sense, but requiring following you specifically from a site for general promotion (meaning posts that have nothing to do with you), will eventually backfire.

However, maybe not. That's why I'm following you. So I don't get booted from promo groups I've been using, and all of a sudden get a threatening pinned post saying if we don't follow you we can't promote our stuff.

Is that the kind of follower you really want?