To reply #1: I agree completely!
To reply #2: I agree completely!
Anyway, to get (somewhat) serious...
To #3 and #4: Yes, I had been looking at the gauge, and although my sense was that fuel economy was worse going up an incline in a high gear, it really was rather difficult to judge that seeing the way the needle could jump around so much, plus I think there's a bit of a lag in it. Hence I was looking for more "scientific" explanations, and I think the idea of the throttle being wide open just causes more fuel to be used inefficiently when the engine isn't generating that much power.
Part of the reason for my asking was that I recall an article in Road & Track many years ago in which they reported research done by BMW. The overall conclusion was that for maximum fuel economy, one should get into as high a gear as one can as soon as one can (no winding out to 4000 rpm and stuff like that) although oddly enough with brisk acceleration but with quick shifts, even as low as 2000 rpm, to get you up to your cruising speed (obviously this is not a technique to apply when entering highway traffic). I was then wondering if the logical extension of that then applied under all driving conditions, i.e. keep the revs as low as possible without lugging for maximum economy. Granted, not maximum acceleration, but maximum economy. On a level roadway, I'd say yes, that's the rule, but efficient climbing of an incline requires more power produced through higher revs, not just by dumping more gas into the combustion chamber.
Thanks for the thoughts!