Pali, thank you for such a thoughtful and considered post. You make a number of good points, not the least of which was the absence of the Luftwaffe over the D-Day beaches because they were defending the skies over Germany or resisting the Soviets in the east. I would suggest that was an effect that was very much in the minds of the senior commanders with which you have such reservations.
Eisenhower was able to reassure those facing the fearful odds of storming a well defended coast that any aircraft that they saw or heard would be ours. Even with such Air Superiority it was a close run thing. If they had been repelled who knows if and when another invasion would be attempted? The Liberation of Europe might then have been completed by the Red Army. In which case the entire population, military and civilian, Axis or subjugated, would have suffered the terrible fate that you so movingly relate in your final paragraph.
Of course there was terrible suffering in Germany, as there was in Poland, Russia, Holland, Britain, and everywhere else that fell under the dark shadow of WWII. Since then there has been continual suffering in further wars, up to and including the present. The concept, if it were ever true, that somehow the civilian populations should be spared the carnage of the battlefield, was certainly debunked well before Dresden, just as it is in the cities of East Ukraine. The only way to prevent it is to prevent war itself.
There is the rub. We know what doesn't prevent war; ladies with wire cutters outside NATO bases, United Nations resolutions, German Chancellors bearing papers promising peace in our time. The problem is we don't really know what does prevent it, other than to carry a big stick and speak softly. As an old Cold War warrior I found that to be quite effective, but that doesn't fit in with the world of today it seems.