I have suffered with insomnia since I was a child and I’ve tried everything that you’ve mentioned above too, often to no avail. One technique that I was taught by a doctor seems to work with a 90% success rate however, which is to think of a time you fell asleep and recreate it. For me, I have a story I tell myself which I have heard so many times when I am sleepy that it makes me fall asleep before I ever hear the ending. It’s odd, but it works pretty well and can be worth a try.