3) According to Rav Moshe the relevance of 3 million is that this is the required population for an area to be deemed as a reshus harabbim. 500,000 people is a very large proportion of 3 million.
7) First of all, they were only asked, at the most, 9 years ago and not as you claim over the past forty years. Second of all, it is not only that Rav Hirsch did not answer satisfactorily he simply missed many points. Third of all, Rav Hirsch admitted to a friend of mine that according to Rav Moshe the Brooklyn mechitzos are sufficient.
8) My point was that many of the arguments are irrational. Of course, if one followed his rav who does not allow carrying I would agree that is rational.