Hey @SCORPION
I'm so sorry to hear that you are suffering from terrifying nightmares or unrefreshing sleep. What a dreadful choice to have to make.
I have had very terrifying nightmares over many years (though thankfully not so consistently as you suffer from). They often wake me up, but it is worse when I can't wake up even though I know I am dreaming. I can't remember what the condition is called but sometimes I am actually paralysed by fear whilst dreaming, and cannot fully awaken until I can move something (usually a finger or toe is all I can force to move with all my willpower). So I can relate a bit to the terror.
BTW the ones reliving the accident are possibly flashbacks(?). These tend to be terrifying even when one occurs when you're awake. You mention that you can't tell the details here of the more terrifying ones (presumably because it would potentially be too triggering?), might it help if you tell us what they are about more generally? I rarely have nightmares these days, I think because I have spent so much waking time facing up to the fears which I had unconsciously hidden away from myself for self-protection.
I wish I could help or offer suggestions but I can't much, perhaps you may find something in my experiences with this that may be of some use. I know that when I am struggling with sleep I need to work at preparing myself before going to sleep, I even have to be conscious about which side I sleep on and trying to relax my jaw and legs, as I tend to clench my teeth whilst asleep (to the point of migraine sometimes, or even breaking a tooth) and press down with my right foot (like it's on the car brake). These are things I've come to very recently to help myself not to be triggered by my body position whilst asleep. Is there a possibibility that something in your room/bed/sleeping position is triggering you in your sleep?
An example is that I cannot handle having anyone sleep on my right hand side, (that's the side my step father got in on), not even my 6yo. I need to sleep facing that way. Even worse when my little girl does climb in for a cuddle because she's had a nightmare she tends to throw her arms around once she falls asleep. I find it incredibly triggering to be touched or knocked when I am asleep. I was starting to become aware of this recently through mindfulness, but reading a book called The Body Remembers by Babette Rothschild gave me heaps of insight and understanding about why; and so some ideas of how to counter it. @Rick can you add anything to this, can you make any suggestions?
You are quite right - trying to function without a reasonable amount of refreshing sleep is like breathing underwater. I really hope something gives soon, and you can achieve some good regular REM without nightmares.
Hope for refreshing sleep endures...
Kindest regards,
Kristin