Jesus made many of his points by asking questions and leaving it to his audience to wrestle with what he had said.
Planting seeds and asking questions is usually much more effective than trying to convince a JW via lecture and logic.
For example, when your wife says you have to obey the GB no matter what, you might ask, "What would you say to a Catholic who said she has to obey the Pope no matter what? What would you say to a Mormon who said she has to obey the Mormon prophet no matter what?" Of course, she would say, "We must obey Jehovah rather than men."
Leave it at that. See if a light bulb goes on. If not, don't press it. Just keep asking good questions as the opportunity presents itself.
If you still believe in God, pray for him to break through the WT's brainwashing and open your wife's mind, heart, and eyes.
If you'd like to chat further with me regarding this, feel free to PM me.