Took kitty in for some follow up blood work yesterday and all the blood values are trending back toward where they should be. Everything still elevated past normal range but certainly more manageable than before.
She's acting a little punky today, so I'm not shouting that we're totally out of the woods.
But the doc seems to be on board now with my original theory that perhaps an infection caused an epsiode of acute kidney failure, rather than this being end-stage of chronic kidney failure. He seems hopeful that when we finish out the course of antibiotics - three more weeks! - maybe the numbers will be in the normal range.