my thought on your sleep disorder: by the symptoms you experience (delirium etc) it sounds like you miss out on the Deep Sleep. No matter how long your actual hours are or what doctors think, your body gives feedback like the one of a healthy person who is seriously sleep deprived for several nights.
skip this alinea, it's sleep theory you know already:
In normal persons Deep Sleep takes the first 5 hours of a night. It's called the non-REMsleep or nREM sleep. If sleep deprived the body will stock up on this sleep pattern first, make it a priority. Person will fall asleep instantly and will go into Deep Sleep asap. No dwindling in other sleep stages.
If deprived for longer times they get delirious. Mad. Dead.
I think you are deprived of sufficient Deep Sleep. Especially maintaining this nREM sleep stage seems to be the problem, it would be the first thing I'd investigate further.
Unfortunately I know not enough of the mechanics of this stage to give you any insight into why or how.
I know a bit about REM stage,
I follow dr. Mallick, and I know for going into and maintaining REM neurotransmitters in just the right mix are everything. I am curing my own botched up mix and insomnia, caused by a DNA mutation (the MAO A you see in my signature)
So I think there's may be something going on with your neurotransmitter mix that prevent maintained Deep Sleep. From your story I understand that falling asleep is not a problem.
the one advice I can give: preserve your energy, you ain't got much of it. Just like most of us.
The biggest energy slurper in you day is digestion so I would urge you to spend as little energy on digesting your food as possible. No raw foods, no fibers, no veggies unless thorougly cooked. Also nothing that upsets the nervous system of most people. Even if tests show your system doesn't flail in the presence of gluten, sugars, additives, alcohol and milk, I would avoid them nonetheless. As a matter of fact I do so myself and it has brought my daily energy up.
This leaves foods like: fat juicy chicken wings and legs -with skin!, egg yokes, chicken soup, coconut fat, rice, pears, whipped cream (ok, it's milk but oh so good), dark chocolate, beef with as much fat as possible, fish, any stock, chips, fries. You see that you won't go hungry and you won't feel miserable "on a diet". Just eat them in small portions.
Other energy slurpers are: showering, cooking, choosing what to wear, dealing with annoying people, noise, worry. You can cut down on all of these. I'm sure you already do.