[hailk]

This might sound obvious and you might have tried a lot of these already, but for me what works in similar situation is that if it crosses 4, I skip sleep that day. And having a strict wake-up time works. Of course as the parent comment suggests, the night light played an important role. I have three different lights near my bed, each less intense. Also having dinner early, cold showers before sleep and no exercises at least two hours before.