I haven't read through the whole thread, but if you're bothered that the pastor posted on the church's FB page, you might say something like, "Pastor Bill, naturally I've heard that your daughter is going to be married, congrats on that! I'm slightly concerned about your posting the registry info on the church's FB page. I don't know how that looks to prospective members who might be looking to join our congregation. Perhaps that kind of thing is best kept to your personal FB page?"
I'm Jewish, not Christian, but in my experience the rabbi is hired by the congregation, so it's not like they have all-consuming power. And since yours is such a small congregation (as mine is), that financial relationship is even more personal.