*The hierachy point is mentioned in the context of the rise to that State Religion and the formation of an established orthodxy, but I can live with how you have it.  
 *Saying "Among Gentile Christians," does indeed imply that diverity existed only among then, and also only because of the "great distances." This is what I think the language in your version does imply, and hence its not accurate.  
 *Assuming there is one correct interpration of Christianity is a POV. We can not make that assumption but only stated that this is what the Christian groups believed. Note this does not state there is no correct interpreationalthough I don't think there is any one correct interpration (religion is not science), but to use a NPOV wording that doesn't assuming the stance of one view as "correct" is required in my view of the NPOV policy.  
 *Yes, there were different Gnostic schools, just as there were different Jewish schools, and among both of them only some regarded themselves as Christians. We we need not concern ourselves here with this level of detail, as the link to Gnostism explains this. It suffices to refer to Christian Gnostics.