Dear me! I relate, if not to everything,to most of what Jon said.
Specially the thing about training your mind to notice the body falling asleep. I'd like to talk more about that, and give you even more tips, if I may say so. But I think you should do like you said, and stick with Jon's tip for a while. If you think it's not working then I'll gladly give some tips.
Strangely enough, I wake up at night about almost 8 times as he said, though I don't know why this happens because I only try astral projecting early in the morning or late in afternoon. I'm really a light sleeper though. Must be it.
Flashes hand, you mean jerking? Because if it is, this happens to me all the time, and that kind of falling sensation too, it's annoying sometimes.
Anyways, in case if you don't have any progress I'll throw in some tips in a different approach to sleep paralysis,but hopefully you'll only come back to tell us you were successful!
All the best (¹ω¹)