The simplest way to get maximum range data is to use fuel flow (and not power). Especially for turbine engines, which become more fuel efficient at higher power settings.
And the maximum range airspeed is for maximum air range, not ground distance. Factoring in headwinds and tailwinds slightly...
The Rotor rocket was only going to use the rotor blades on descent. There was no way it could lift the loaded rocket. The blades were tip jets powered by peroxide (I believe)
Hope that helps with your question.