Good essay Terry, thanks for posting it.
I have to agree with Trevor on the points he makes too. I don't think the 607 date is the achilles heal of the org we'd like it to be or the tipping point for the vast majority of JW's.
You're a very intelligent guy Terry and for people like you and a lot of people on the board scholarly subjects like this are very important but I think you over-estimate the intellectual capacities of the majority of JW's.
IMO the vast majority of JW's are uneducated to the point of ignorance but extremely self satisfied with their 'special' knowledge. Ironically they think they are open minded and that they 'test out' the information they are given but it's an illusion as the only references they use are from the same source. Any opinion that conflicts with that 'special' viewpoint is obviously wrong.
Also the society has been quiet about dates specifically ever since the generation change in '95. If you mentioned 607, 1919 or even 1914 to the 1.5 million who have become JW's in the last 10 years or so you'd get a blank expression and they'd struggle to explain the significance of those dates.
As has been mentioned the majority of JW's leave the org because of personal issues. There aren't many who leave on doctrinal issues because they're too weak intellectally and emotionally through being cuckolded by a selfish organisation who they fear displeasing.
Where I think the 607 issue is very useful is for those who have been JW's for some years and remember the 50's, 60's and 70's, and for whom '75 still leaves a bitter taste, when predictions, numeric charts and more indepth articles on subjects like this were being published and were given great importance.