I've really enjoyed reading your posts when I was lurking (and now of course)! You have a really nice way of framing arguments and I'm not suprised that you were able to make converts (both in the org and now out of the org). Some folks are naturally convincing. I'll bet that you're in a sales/marketing position.
I don't know his entire history, but to answer your question, I'm not aware of his converting anyone. He was a regular pioneer for quite awhile. But, he's not a very good communicator and I personally think that's who gets the most converts. I know another brother (he's older now) who has probably brought in excess of 100 people in. Why? I don't think its because of his understanding of doctrine. Its because he's a great guy, easy to talk to and yes is absolutely sure he has the "truth". But, its his conviction that really makes an impact on people. Not a creepy, brainwashed type of conviction. He is very genuine and when folks are having tough times in their lives, he is easily someone you instantly trust. But, ask him to explain what the WT teaches about Rev or Daniel, he doesn't know.
So, doctrine is important to the organization, but unquestioning loyalty is really how they hold people. To me, the folks most likely to leave are ones who really understand the doctrine. Those are the ones that say, "what just a minute" when "new light" is released. You & I are about the same age. So, the biggest change in our lifetime has been the generation change. Many in the congregation I was in at the time didn't think much about it. It bothered me for a long time.The only ones that grumbled were the ones that I considered very knowledgable about doctrinal matters. If the Society were smart, they'd make a few more changes to push out completely folks like me who are interested in understanding complex teachings and who are more aware when changes take place. They'd end up with a slightly smaller but even more easily controlled base. Although, they sure do a good job of controlling things right now.
The only problem I see, and to your point, is that the ones that really understand and believe the doctrine are the ones who are the backbone of the congregation, surely your parents fit that category. So on the one hand, folks that know the details are more likely to get upset when something changes. But, they're the ones doing the bulk of the work. For the rest, they're happy not understanding everything but they're not willing to make too many sacrifices. Its a tightrope and eventually, they're going to fall off.