Northener here. I don’t mean to take away from your point, because you are mostly correct, but my school at least did teach us about the harrying, though I can’t remember how much detail, but it was at least a few lessons on the aftermath of 1066 and how the Normans took control.
I will mention (mostly because I find it funny) that I remember hearing about a planned revolution in Britain (around the time of other European revolutions) that was called off because of the rain.
My understanding of it when I read the books was the spice gives them similar prescience abilities to Paul. Effectively allowing them to see what’s ahead and navigate before it’s an issue. Especially because they’re flying faster than light so they can’t rely on their eyes as they’d crash into something by the time they actually see it.
I have a hazy memory of the book explaining they were once humans addicted to spice, so presumably they have some controls.