On the issue of the atomic bomb, I should point out it took until April of 1941 that efforts to develop it as a weapon, instead of as a propulsion system for submarines, truly began. From then on, any number of things can happen to derail the project or prolong it, so to assume that combat deployment will definitely occur by August of '45 shouldn't be taken as a article of faith. Even presuming such does occur, the maximum altitude of an unmodified Flak 88 was essentially the same as the maximum altitude of a B-29; I think that should be clear as to what it means about efforts to achieve mass nuclear attacks.