I changed it again. The Josephian Heresy. 
Interestingly, it took the Catholic Church until the late 1900s to apologize for and clear Da Vinci of heresy. There won't actually be too much detail in the book about what the heresy is, but it won't be an improvement. As noted in a previous post, most of the heretical ideas will result from Joseph unwittingly working with a demon in his head, which he thinks is an important religious figure. I haven't picked one yet, but that figure will replace Jesus in Joseph's head. I'm thinking maybe Moses. I also have to think about what the new heresy will be (in v3 it was the idea that Joseph was the child of Jesus and Mary Magdalene in a former life). There's some funny material in v3 between Joseph and Jesus, so I hope I can save some of it.
The Josephian Heresy is intended to be for the whole galaxy. God tells Joseph that when he's still four years old, which you previously read.
The Christian church remains very much intact. In fact, the major denomination of the church in the galaxy is on New Bethlehem. But "God" told Joseph that the Josephian Heresy is needed since there are 50B people in the galaxy, most of whom are non-Christians. New Bethlehem only has 100M people. And I have yet to decide if I'm going to add a Catholic planet (New Vatican) or just the woke planet (New Canada). For every Realm planet I add, I have to balance it with one Imperial planet for the kids to visit too, so two Realm planets (New Vatican & New Canada) would require two Imperial planets, which is too much additional material. Potentially New Vatican could be a non-aligned planet, so I'd only need one extra Imperial planet.
Or I could make New Bethlehem a unified Christian planet (no more Catholics vs Protestants). Or, maybe they're like Northern Ireland, at each other's throats. That would be another good reason for God to intervene with the Josephian Heresy. One idea for the heresy is that Jesus won't return until Catholics and Protestants reconcile. Perhaps Joseph's life's mission is to bring them together. I like that a lot.