RE: The illusion of political division: Take a step back and understand why we constantly disagree
You have laid out how pretty much all human endeavour that veers even slightly from the brute material realm is a house of cards built on foundations of clouds and sand.
The more of life I see, the more I engage in arguments with people who, while clearly competent and intelligent, have beliefs that are utterly incomprehensible to me, the more I realize that:
i) reality doesn't care what we think
ii) our thinking doesn't care about reality
What I mean is, our brains only barely interface with reality, they interface with a Cliff's Notes loose approximation shadow of a shadow of an image of reality. As a result, we can believe almost anything (aside from stuff like: "humans can fly" and "gasoline is a nutritious drink") and still be functional members of society.
When you look at the human world through that lens, it's a a wonder we have even built a society at all and held it together for this long. We are all of us mad and full of worlds.