I can very much relate to all your descriptions...!
So I've wondered more than once if my body has a problem processing/utilizing iron and oxygen even though I have adequate levels of it.
Might be a useless rabbit hole, but Morley Robbins aside from touting magnesium believes that we need a good specific copper form to get the iron going.
I've had orange spots increasing on my lower legs and feet the past 2 decades, actually tending towards big orange areas, and some of my docs believe they might be iron deposits. My iron blood levels have always been normal. The past 2 years the spots have been greatly decreasing again, I believe from my supps. Maybe copper, actually, cos it was low, and I increased it fairly quickly, whilst it's "antagonist" zinc was always high, so I only took zinc until I knew this, and only took copper till the level was above average.
By the way, the nimbleness that LD N gives me doesn't feel quite normal either, it feels light-limbed, analog to light-headed. I don't know if that's just cos I'm not used to it at all, but it doesn't feel just like the limb heaviness having stopped for long periods. Or whether it's the "fakeness" cos it's often contradictory when I have its energy but am not able to use it fully, cos I get "ill" if I do. Either way I just enjoy it, like I enjoy light-headedness when I have it.