Hello, Mark, and welcome.
Thank you for your thoughtful post.
I think that "ultralight backpacking" spans an enormous range of people and techniques (so does "survival" for that matter). Some of it borders on nuttiness; most of it is a worthwhile endeavour.
Loads can be pared down quite a lot based on experience, diligent research, and planning.
I've been solo backpacking for a couple of decades, and I think the "solo" part makes me more conservative than some. I'll pare away every possible ounce (an endless obsession with backpackers); but I want a stout safety margin in case something goes wrong, in case of a freak snowfall, an injury, etc. etc.