Been struggling with this for (1 - 1.5) decades too. I don't have a answer yet, but I think it's just a matter of (more) time until I figure it.
Melatonin fails at any dose/pattern, it's too weak, it only aggravates the following day. Inhibitory steroids help a little, but not nearly strong enough to adjust the cycle. Glycine puts me to sleep for about 2-3 hours, then I wake up wide-eyed and not a thing will get me back (I seen a few other reports of this problem, no real explanation, and one or two people reported it became permanent! this happened to me in the beginning but it went away). NAC keeps me awake. Antihistamines don't work out and too many side effects. No luck with prescribed stuff (quetiapine, trazodone, benzo). Combinations unsuccessful.
The only thing I've found out so far is that you absolutely cannot have a Vitamin A deficiency trying to fight this. It's tightly involved in circadian rythm regulation. Basically eating liver 1-2x/week prevents that and it becomes easier to wake up and survive despite the struggle.