Hello Paul! You are already using the shortest sleep window and there’s really no need to change anything.
I think you have the wrong concept about sleep windows. It’s only there to help regularize your nights and keep your sleep consistent, but at no means, does it guarantee you will sleep. Obsessing over the details and asking too many questions is probably not going to help you very much. Your best sleep happens when you don’t obsess over the tiny details or wonder if you are doing it right. It is in letting go completely and letting your body take over.
In a way, your sleep window questions are like asking if you eat your lunch at 1pm, will you get hungry enough at 7 pm for dinner or do you need to eat lunch earlier so you get hungry by 7pm, or something along those lines. The answer is does it really matter? Does it matter if you eat lunch at 12pm, 1205pm, 1230pm, or 130pm or 2pm or whatever, are you so obsessive in getting hungry enough to having dinner at 7pm sharp?? When you start doing things like this for everything, you only create unnecessary hassle, inconvenience and disappointment to yourself. And when you don’t achieve your desired result, you begin to despair over it and think something has gone wrong somewhere and start doing different things in an attempt to “fix” it, when you really should just RELAX and let your body do its job. Your body just knows how and when to sleep in the same way as it knows when and how to eat, breathe, plus many other functions. Obsessing over details is pointless. You get sleep when you don’t think about it or even want it (think about those time how sleepy you got when you were stuck in a boring movie, a boring lecture, or just plain bored from doing nothing). People desperate for sleep and wait all day for it to happen just don’t get very much of it! Learn to appreciate the overall process and not the outcome, stop chasing sleep and take your time to appreciate the other things in your life. Hope you find this useful and good luck.