Very good write up by Darrell.
75% load is not 75% throttle. You'll need a scangauge to calculate load, or a vacuum gauge. 70mph will hurt the mileage quite a bit. Even dropping 5 mph will get you 10%+ better mileage.
I agree with all his info except I use a different technique on hills. I tend to pulse up them, stop accelerating near the top, loose some speed before I peak them, and then use the downside to accelerate back up to speed (w/o the engine if possible).