I didn't question the JW perspective on 607/587BC when I was in, and it didn't matter to me afterward. The back-and-forth I see here is similar to what I've seen elsewhere, and I don't have the understanding or the patience to work through it. I also think it is moot.
Russell used the 1914 date to indicate the end of the world. Not the start of the end times, but -as Stephen Lett might say- the end of the end times. I think that his belief was that Christ's heavenly reign had begun in 1799 or 1874, and that 1914 was when everything would be complete and the new system was to begin.
It took some time for Rutherford to update the teaching, so that 1914 was given new relevance. It was still a useful date, since WW1 had begun that year and it could be used as evidence that Russell was on to something. The date could also be used to keep the pressure on through the use of the 'generation' teaching. Now, it is more problematic than useful, and I don't see that the issue about the dates will matter much longer. I even wonder if, at some point in the not-too-distant future, the WTS will accept the 587/586 date and pretend that the debate never happened.