That "checked them on a hunch" part got me because I always figured tire pressure was one of those things that barely moves the needle. Then I actually tracked mine for a couple months and saw the same kind of jump you did, like 2 or 3 mpg just from air. Now I check them every time I get gas, which sounds annoying but takes two minutes at most.

Idk man, is a travel journal setup really the thing that fixes airport chaos? Sounds like the chaos was just you having too much loose paper, and any folder or envelope would've done the same job. Maybe it's just me but this feels like a solution looking for a problem, like the trip was fine and the notebook thing is just something to feel organized about. I've done plenty of layovers with a random ziploc bag for receipts and it held up fine too.

Squinting is the oldest trick in the book and it still beats half the tools out there, since it strips away color and just shows you value. I do the same thing with the blur filter in Photoshop when I'm not near a printer, and nine times out of ten the thing that fails the squint test is the thing that would've failed on paper. Your contrast checker only measures the numbers, not how the eye actually reads the page, so trust your squint over the software.