The Vref+20 scenario is at flaps 25 vs flaps 30 ("stuck stab" scenario). However, there is no adjustment in the tables for flap position, except for resulting approach speed.
If anything, flaps 30 would shorten the landing roll slightly (due to higher aerodynamic drag), making an even larger difference betwen that and the 320 Ton scenario.
I don't know about brake energy or torque limit effects. But the "pull you off the simple mu relationship" factor is EXACTLY what I am trying to bring out here. The simple equation cited by hawk37 may look good on paper as a basic equation with simplifying assumptions, but does not reflect the reality of stopping different size/weight airplanes with different brakes, tires, footprints, tire pressures, etc. The fact that such a substantial difference can be readily illustrated using 2 IDENTICAL airplanes is a clear contradiction of hawk37's premise.