Hey Falcon,
Sump isn't off yet, it's really stuck on one side still (side closest to front of car as engine is tilted up and hard to get any leverage on).
The whole oil pressure thing just goes around in circles, hence why I didn't bother with exact figures, there's a wide range of variables that come into it and in my view Toyota is telling you the safe range.
I don't quite understand the big end/sticky tires comment? Are you referring to the extra load placed on the engine? Is the shimming of oil pressure relief valves a way of raising oil pressure?
In terms of kms, the car has about 200k kms but the engine is rebuilt (the car has an interesting/somewhat unknown history) based on a number of observations I've made. Hence dropping viscosity a bit; partly because I feel it's a fresh engine and just to see how I like the viscosity/brand (trying Nulon)