I have had a similar "cornerstone habit" for several years now, with the same underlying assumption: if I can get this one thing right, the rest of my goals and habits will fall into place much more easily.
However, I've formulated the habit slightly differently:
Turn off all devices by 830pm
I have an alarm on my phone that goes off at 820p to let me know all devices need to be powered off in 10 minutes. That means no phone, no computer, no TV, no iPad, etc. The only exception is my Kindle.
What I've personally found is that if I don't have any devices to distract me, 90% of the time I'll start to get sleepy before too long. This makes going to bed at 9p or 930p so much easier. This is especially true after my body has adjusted to a week or two of going to bed early and getting up early. I do occasionally get stuck in a book and stay up late reading, but it's pretty rare, and I don't usually have that stupid addiction feeling I get with Hacker News or Reddit where I'm not even enjoying myself anymore but I just can't seem to put the phone down and go to bed, even though it's 12:30am and I wanted to wake up early.
Previously, when my goal was to get up by a certain time or to get a certain amount of sleep, I was in a constant war between two versions of myself: the one that wanted to stay up late and the one who wanted to get up early, get more sleep, etc. Shifting to just turning off devices at a certain time in the evening has proven to be a lot easier to conform to and still get the same end result.