This was all very interesting when people came up with their various doomsday dates, but it is quite easy for a JW in later times to simply think that "a year is a year" and just as the Jewish calendar allowed a variance in the year once in a while to correct for errors, so a cult member would accept the theories that allowed for a proper year to be used.
I know that isn't really an answer, but it is easier to demonstrate that 607 BCE was wrong and that Watchtower predicted so much for 1914 CE that did not happen, and even easier to demonstrate that Watchtower and its predecessors has said the sky is falling so many times when it didn't.
This stuff is important to only a handful of us- most of whom are OUT of Watchtower. As for the rest, they already KNOW that C.T.Russell was right even though he was wrong. So further complicating the dates doesn't seem like a way to help them wake up.
Here's some simple math- Russell believed that Christ had returned invisibly in 1874, and that he had been ruling from heaven since that date. He believed and stated that the "Gentile Times" would end in 1914, and that Christ would take power of Earth's affairs at that time. That was ONE GENERATION of 40 years past 1874. The only reason 1914 is held onto within Jehovah's Witnesses to this day is because World War I broke out that year. But that was not the thing they were looking for, and if it was, it should have led to Armageddon instead of peace afterward.