About suffering, it's everywhere, sadly. I think most of life is suffering. Our own life is likely a mix of suffering and pleasure but if we view all life (not only humans but other animals), most of it is suffering. I think the way out of this is by intervening in nature, as nature has a lot more suffering than humans themselves do or have even caused. Look up David Pearce or even Peter Singer. Pearce's "The Hedonistic Imperative" was written in a very hard-to-read way, at least for me. Like, I had to constantly re-read sentences and look up words. Nevertheless, I loved his ideas. Singer's ideas are also worth considering. What I remember from reading Pearce and Singer years ago is that there's a lot of suffering in the world, that humans' suffering is just at tiny bit of it and that we should strive to reduce the overall suffering. It might sound like a pipe dream to intervene in nature - someone will say "we'll only make it worse". And probably right now we will, but I believe we'll reach a point where we can actually intervene adequately.
Zapffe makes interesting points but are too close to what I consider attempts to describe human psychology through vague philosophy. Yes, isolation, anchoring, etc. may be useful things to talk about, but his philosophy, at least from the minuscule amount I've read, doesn't discuss suffering generally (using terms and ideas like qualia, etc.), doesn't extend suffering to non-human animals and doesn't offer much of a solution beyond some psychological changes we can implement (which could only benefit humans).
But I love that you're focused on suffering. It sucks and it's the thing that sucks the most and that could suck the most - by definition, even. I rarely find people acknowledging suffering as something to eradicate. It's usually something more specific, like a problem with economics or unions or tech or mental health. But all these lead to suffering and suffering is what matters in the end.
I have yet to reread the rest of your post and reply (as I don't like to just reply immediately).