The conventional wisdom is no caffeine after 4 but the half life is 4ish hours I remember reading somewhere. It’s better to hard stop caffeine consumption before 2pm.

I think blue light also conflicts with your body’s natural sleep priming so yeah cutting screentime before bed is a win or at the very least use the night mode or orange filter on your phone after sundown.

If your schedule is really bad, an acute solution is to hard reset by full commiting to going to bed at your new desired bedtime. Don’t nap or anything that day if you can, and if your desired bedtime is too early you can try taking some melatonin. Don’t use melatonin regularly though.

That’s how I wrangle my sleep schedule back to a better baseline when it starts to drift towards later nights and waking up exhausted.