That said, if you do think the Book of Mormon is so unreliable and imprecise on anything non-doctrinal, then I think you would need to be consistent with that, and give up all the LGT nonsense. How can you cry unreliable about anything that goes against your case, and then throw out theories based on mathematical models of population growth?
Nephi, Moroni, Mormon and other authors did not just sit down with a calendar, a map, some demographic lists and a check list of doctrines and wrote stories constructed on pure data with a bit of doctrine thrown in when an event seemed to fit it to make a tidy sermon. Instead they crafted their own sagas that Mormon gathered into an epic, all with purpose, with meaning and to do so required much more than a calendar and all its handy datakeeping fellows that told what they were doing when along with a few choice thoughts they had slapped down when they had the time. The book most certainly doesn't read like that.
Instead the dates, the times, the locations, the wars, the events, everything used by a storyteller to construct the scene are used to create the proper setting for the ultimate creative goal....which is to show the world the results of God acting in concert with Man and what happens when their partnership suffers due to the pride of the mortal side, when they choose instead to cultivate ignorance in the divine, it is a story with a grand scale that is tragedy with constant failures and betrayals, even of those near and dear, but also ultimately a victory of love for those willing to trust in the future because they trust in God and lay their very lives with all that means into God's hands to do with as he would.
The reader will learn what is and isn't reliable by reading well enough to determine what the writer is trying to convey to his audience, what the purpose of his text is. If the reader decides it is a military text, numbers, locations, strategies will likely be quite accurate in order to fulfill that purpose. If the book is to be a anthropological text to examine the culture and interact of the humans within it, then it would be likely that the text would concentrate on every day human actions and events, status symbols, festivals, etc.. If it is a text that is to present how man interacts with God and God with man, if it is to testify to the reality of that relationship over time, then it is likely to present covenantal relationships and how those are played out, doctrinal teachings that elaborate on the relationship and how to refine and develop it, expectations for what one can expect...predictions and blessings and stories within the story demonstrating how all this plays out in real life both in ways to emulate and ways to avoid. Look at what is meant to be achieved by such a text and I can think one can find where the most effort would be put to ensure the book had a reliable core while perhaps some of the more peripheral parts might be used somewhat creatively/symbolically by the author to add emotional or other support here and there or to draw attention to a crucial moment or other secondary part so that his overall structure is both balanced and dynamic to draw the eye and heart and soul and above all to make one think of God and that covenant relationship he offers all so that when the testament has been consumed, the reader is now a seeker of God as were those he read of, attempting to emulate their path in his own life.