Not sure this belongs in gear deals, but think your reflections very interesting. Will use "watch this thread" and hope it works if you move it. (to Gear?)
Have you considered getting a two person quilt? Enlightened Equipment is now making them, and I've ordered one which should be here soon. Anticipate shared warmth will really up the efficiency, and of course, more importantly,...
Agree that food is mysterious. For me the magic food is high quality salami. No dithering about do you like your salami sliced thin or thick? Just bite its head off. Allowed me to go cookless for 9 days, but I lost 10 pounds. tortillas, cashew--almond butter, dates, brazil nuts, electrolyte replacement drink, also favorites.
Have been cold in my Zpacks 20 deg., temps in the mid to high 20's at altitude, in a bivy sack, hours spent awake. Sleeping pills sound hard core! Had a neo-air, think I needed something warmer under me. Not sure about the Zpack foot design --0 loft where everything comes together down there.