DS6 has been having a terrible time falling asleep, staying asleep, and going back to sleep after he wakes up in the middle of the night. For the past year or so, he has slept face down in one of his baby blankets, with a top sheet wrapped tightly around his head and shoulders and tucked in all around him to protect him from monsters. Now, this position is no longer comfortable to him, but he refuses to go to bed any other way. When he can't sleep, he panics and and cries out for us. We've tried talking to him, sitting with him, letting him cry it out, letting him sit up and read, but nothing seems to help. The one night we let him read at 4 am, he never went back to sleep and was of course exhausted the next day. Because we can't make him sleep, by the end of the night everyone in the family is frustrated, angry and exhausted.
My heart really goes out to you. Our DS8.5 seems to be just "growing out" of this phase in his life and I believe you about how exhausting it can be. He still sleeps with the covers pulled up over his head, even in the baking hot summer temps we have here although he is generally outgrowing the fears slowly. It took a total of 6+ years for him to feel confident enough to sleep through the night in his own room.
It helped a little that we have a good alarm system and he is able to visibly check it every night before he sleeps. I second masterofnone's suggestion on physical activity. I'd like to add dietary considerations too. We added some omega3 and lots more fresh fruit to his diet. I have been concocting fresh fruit and vegetable juice recipes (and he helps me so it's become a fun thing to do) so that he can get more vegetables in his diet without cringing about the taste. And it helps him to have something light in his tummy before he goes to sleep as well.
We have a mattress in our room for him to come to whenever he feels like he needs us. Even these days outgrowing this, we still keep the bed there. It's always made up with pillows and blankets etc so he can sleep there whenever he needs to.
He has a little soft toy puppy that he talks to all the time so puppy goes with him everywhere (we homeschool so bringing it to school is not an issue for us). Gives him comfort. Night light and flashlight within easy reach in his bedroom. Lots of hugging and holding.
I remember feeling the fear when I was that age too. I'd sleep with towels wrapped around my neck because I was so afraid of vampires. It may take him some time but I don't know what else to add other than these suggestions, support and understanding.
Take care!
