After taking a quick glance, my first thought,
why only a post office box?
Why not physical address?
When I worked in radio, and we sold a program, we required a physical address if the mailing was only a post office box.
But they are itty-bitty in comparison to orthodox catholicism.
The fact is that there are more and more splinters in protestantism all the time.
All claiming to be 'bible-alone' believing churches.
I'll bet the church in the OP is 'bible-alone'.
The point is no matter what Christian Sect you are a part of you have divisions.
And you over play the itty bitty.
If the Catholic Church is as is claimed the universal church of the 1st Century then all the elitist that came out of it formed the entire gnostic movement and how many gnostic movements were there?
quite a few.
Then then you get down to the Montanist who were elitist as were the Donatist. Then the copts splintered over the Monophysite view and monothlythite, You have the Assyrians splintering off of the Christokos view, not to mention the filioque almost caused a splinter with the eastern churches, then you did have the schizm due to primarily Romes mishandling of the issues.
Then during the middleages you had many sects split off from the Catholic Church that an inquisition was needed.
Finally you get to the Reformation and the protestants.
Who are not original in having many sectarians.
Plus you forget pius x and old catholic out of Ultrech.
For the most part, Old Catholics only 'protest' the authority of the pope.
Same for Anglo-Catholics although many of them are either at the banks of the Tiber or have already taken the plunge.
Pius X is being reconciled to Rome.
I believe the question really is, 'what is orthodox catholocism?'
Which of the schismatics you listed would you consider outside of orthodox christianity?
When you add up all the Copts, Orthodox, and Roman Churches (orthodox believing) compared to the number of schismatics you get the picture.
The I don't know Copts have a monophysite view that sounds outside "orthodox" christianity.
The fact is no matter what christian group you are talking about you are going to have schizmatics from that group.
It has always been the nature of Christianity.