Hi BBG, situations such as this would appear to me to aright themselves regardless of the possible outcomes. He's a senior citizen now and most assuredly has already made up his mind long ago, and quite honestly, I don't believe an individual with that much time on the planet will invest the required energy to abandon his lifestyle, even if he does come to the realization that there exist something rotten in Denmark!
I wouldn't however stop extending yourself to him so that he may have the most accurate reflection as to who you are and why it is you no longer believe as the witnesses do, and yes, I too believe that one should try to bring the truth out to those still in, but only to those who are able to handle it. That's a determination you have to balance very carefully. To sow seeds of truth about the truth to those not in a position to handle all the serious ramifications that come with such knowledge, in some cases, you might be doing more harm than good.
Somethings are Better Left Unsaid
art