I have become enamored with the idea of hunting deer with a light kicking, flat shooting, smaller bullet.
All the ballistic minutiae in your post is irrelevant on deer inside 300 yards, or even 500 yards... the above the salient statement in your post.
Though the 260 answers what you want, I think the Creedmoor would be an even better choice.
My sense is you're overthinking this... whitetail deer are just not that tough, any of a 100 cartridges will work to perfection.
Might as well use something that doesn't beat you up. My favorite used to be the 250 Savage...
