Quite an amazing conversation, I am very impressed how you were able to turn it into a personal conversation on your own views of the organization. It is a damn good idea to hammer on the cartoons. If they don't sit 100% well with him, he is going to have you in the back of his .every.damn.time. they play one of those at an assembly or meeting.
I have almost been hoping to talk with some witness, however they seem to never be around where I live for the past few years.
A thing I might have done differently than you would be that the comment the books were written by men would be too good to let pass. I think an important followup is "So you say we cannot trust something that is written by men?" with the intention of immediately moving on to ask who wrote the literature he is offering and then go on to question him when one can trust something and when one cannot trust it.. the fundamental hypocrisy of rejecting evolution without having studied it is I think the biggest weakness of most JWs.
Are you familiar with Anthony Magnaboscos youtube chanel?