I appreciate your # 1! And let me start by addressing your # 3.
It is true that there are some aspects of "suffering" that I believe this "integrative vision" can help alleviate: the suffering that comes from a feeling of collective guilt and/or species self-loathing because humankind has brought so much destructiveness and ugliness into the world. And perhaps the suffering of despair that can come with the (unwarranted) conclusion that we are not capable of being anything less ugly than what history shows.
But the relief of suffering is not necessarily the main benefit that I think it offers. For one thing, I've had at least a big piece of this perspective -- that part I call "the parable of the tribes" -- for 47 years now. And I've suffered plenty. Seeing what I see isn't necessarily fun.
But there are important benefits that I've derived, and that I believe many people can, from this "way of understanding." I'll be expanding on that shortly--i.e. in installment #6 (after #5, next, presents "the parable of the tribes"). I'm planning to introduce #6 in these terms: I realize that people reading this series are being asked to do a fair amount of work, and here are the possible rewards that make it worth the effort.
These benefits are less about being relieved of suffering than about plugging into sources of deep fulfillment. At least, that has been true for me in my life, and I think the same could be true for other people. So, stayed tuned.
In terms of your second point -- whether the parable of the tribes itself might offer an explanation of the world's neglect of that idea since its publication -- I haven't really seen anything along those lines. But Philip Kanellopoulos has sent a comment that addresses your question. Here's what Philip has to say.
It seems to me that the Parable of the Tribes might itself predict that it would likely be ignored or perhaps even suppressed by society's centralized propagators of culture, at least as long as the parable remains in force and thus just at the very time the insights it offers are most needed. The parable could hardly be more profound or important. However, unlike similarly monumental shifts of paradigm in recent centuries -- Newton's, Darwin's, Einstein's -- the Parable of the Tribes doesn't serve dominant systems of (state) power and indeed threatens to undermine them and their perceived necessity.
A general acceptance of the Parable of the Tribes is desperately needed as we face the twin existential threats of nuclear war and climate destabilization. The parable promises to rehabilitate our understanding of human nature, offering us good reason to have faith in who we truly are, to believe we just might deserve to survive after all. It also offers us hope that the worst nightmares of history have a situational cause we might actually resolve. An inspiring and widely held faith in human nature -- or lack of faith -- may mean the difference between our willingness to survive and flourish, and our succumbing to misguided despair and extinction. Yes, the Parable of the Tribes is indeed a Big Deal.
My immediate response: One tragic result of humankind's creative departure from the natural order: global warming as the result of human action. The Paris climate agreement, abandoned by President Trump, is just one international step forward to reduce a catastrophic global temperature rise. The accord came very late in the climate change game, the commitments of almost all the world's nations are currently not enough to adequately stem the damaging temperature rise, and it's not known whether new commitments will be of sufficient magnitude to do the job.
The only way humankind will survive this warming, without deep privation, is for a sufficient number of fallible human beings to achieve a level of compassionate concern for one another and for succeeding generations. Bold steps toward drastically reducing our output of global warming gases would almost inevitably follow.