3. You’re holding the Book of Mormon up as something it never claims to be, i.e. an accurate portrayal of ancient history and then criticizing the work when it fails to live up the faulty premise you’ve superimposed. More significantly, you’re assuming that God’s primary purpose in inspiring Joseph to bring forth such a work was to present the world with an accurate retelling of the distant past. In terms of scripture, neither the Bible, nor the Book of Mormon adhere to the fundamentalist assumptions you hold.
Then shall we assume that the Book of Mormon is also neither an "accurate portrayel of ancient" Christian theology, of proper baptism, rites of Christ's restored religion in the America's and all the other theological teachings of the Book of Mormon that the church has incorporated into its "restored church"?
That is the problem of reducing or distancing the necessity of the literal teachings of the Book of Mormon; you risk the same arguments bring applied to its theology and teachings (which are held as sacrosanct and infallable) as you do its "history".