I am glad you understand what you are up against and are trying to move on.
Of course the best thing would be if he could leave, but that's a hard one. If he really knew the history of the religion he belonged to he might see that it is not at all what it claims to be. The problem is that Jehovah's Witnesses have been conditioned to suspect and not believe any thing that is critical of the Watchtower, and that goes double if it is from former members, as we are considered "mentally diseased apostates". This is how cults work and why it is so hard to break free. Even after I left the religion I still had some of this thinking, because it took me eight years before I felt comfortable enough to talk to other former members, I still believed the lie that they were all bitter vindictive people who want to destroy the faith of JWs. You can show a JW direct proof from a major newspaper that the Watchtower lied and they will say it's just a trick of Satan, it's hard to combat that kind of thinking.
If you are interested, I have compiled a list of suggestions on how to help people break free of the Watchtower. It's compiled from various posters who have been successful.
https://www.jehovahs-witness.com/topic/5729160790016000/guide-helping-other-break-free
It has some ideas on things to talk about, some information on cults and how they work and shyly me references.