The Clefairy data is very helpful!Of course, if we wanted to restandardize our tests to be at lower levels (closer to 45-50 than to 50-60), I'd be happy to, and that would certainly bring my tests/observations closer to yours.
That being said, if it's possible, can you try and get your levels to 45-50 in future runs? While you aren't breaking the rules by going above 50 or so, In two of my runs I was generally 50-52 throughout the League, and nowhere close to 55 or even 60. Usually, my 8 Rare Candies (yeah, I usually only pick up the ones I see naturally rather than hunting every last one) close the gap from my team roughly being at level 48.
Additionally, I don't think we should be fighting every trainer, even though I said we need to in the OP. Really, you can skip the Seafoam - Cinnabar ones (though.I fight a couple if I need filler EXP at the very end) AND the Lavender - Fuschia ones, though I have done the latter in my first run - it was probably helped with my Pokemon in the Slow EXP group (Snorlax, Gyarados). Generally, I fight about 80% of them, including everyone in Silph Co. I think I also skipped some Mansion ones in my first run?
As for wild grinding - I think it's only really a thing you should need to do pre-Rival 2 (you have no Repel for Mt. Moon, some mons you catch pre-Cerulean need levels for Rival 2) but other than that it is likely only an occasional thing to top levels off, as the midgame has plenty of mooks for a reasonable team.
TLDR: don't feel the need to hunt every mook down, and let's try to have level 50s around the Elite Four if possible.