Hi J-DUBBED, Keep it simple and proceed very slowly with your son and his wife. Let your son do all the work trying to prove to you that the WTBTS has the truth. All you need to do is ask him simple questions to reach his authentic persona. The best thing is to listen to what your son says. Take your time, read information from cult-exit counselors like Steve Hassan's books (i.e., "Combatting Cult Mind Control", "Releasing the Bonds: Empowering People to Think for Themselves", and (his latest book) "Freedom of Mind: Helping Loved Ones Leave Controlling People, Cults, and Beliefs"), make your plans with your wife, practice with your wife, and then little by little ask your son simple questions.
If you ask questions, your wife should listen to what your son says (or secretly record it with your cell phone) and then you can plan what to say to your son the next time. The most important thing is to let your son do most of the talking and do not explode at him. Yes, the WTBTS is full of BS, but telling your son that will not help him.
The WTBTS has taught JWs though-stopping platitudes, like "Where else shall we go?" Learn to overcome those thought-stopping platitudes within a few seconds, like "Don't you mean to whom shall you go? Simon-Peter said to Jesus Christ in John 6:68-69. What else has the WTBTS interpreted differently from the Bible?" At first occasionally overcome thought-stopping platitudes that your son uses. Overtime when your son's authentic persona uses a thought-stopping platitude, overcome it more frequently.
Also, read the thread by Billy the Ex-Bethelite thread exJW Psychology 102--How to Ask a Question When Questions Aren't Allowed. After your relationship with your son has improved a lot, use Billy's methods when you want to ask really controversial questions of your son like "This guy I know thinks that the Watchtower are a dangerous cult, because JWs will not independently examine their own faith as they preach others do and critically think for themselves. JWs are hypocrites for telling non-JWs to keep an open mind when they won't do the same."
Peace be with you and everyone, who you love,
Robert