Every man, woman or child who ever lived with a batterer,or molester knows you cannot change people. The Jehovah's Witnesses are learning to their incredible embarrassment that they cannot 'change' hardened pedophiles who in fact may have been attracted to their organization in the first place because of this vey view.
What you can do is ascertain the reason your wife is interested in Witnesses/Witnessing in the first place. Nobody just wakes up someday and decides to become a member of this religion, including many people who were 'born' into it. Something is missing in their life, and they think the Witnesses have it. Does this person feel (rightly or wrongly) that they are not loved enough, that their opinions and feelings don't matter enough? You have it within your power to see if this is so, and maybe help your spouse find these thing. How about encouraging the spouse to take up a hobby, or go back to school, or maybe move or remodel or redecorate the house, anything distracting. I know for a fact that works!
Something that works unbelievably well is compromise. Remember, JW's tell eveyone that all non-JW's are under Satan's control, that they will be persecutors, that they're going to die,die die. I have known 'mixed' couples to agree that the child/children can go to the bookstudy because it is in a small family environment and is only an hour. Some have also agreed that a child may attend the public (often Sunday) talk because it is only 45 minutes.
These compromises gives the 'other mate' the opportunity to 'Witness' in their own way, because 1) this tells the mate and the other JW's that hey, I thought unbelievers were persecutors for Satan,what's up here. This puts you in control. 2)it teaches the child that there is another way besides the JW's, and that it works as well if not better. (In my personal opinion, the public talk and the bookstudy are the weaker spiritual food anyway, your best shot).
Those are just examples, and I have personally seen them work, and I have used these techniques in my own family with great success. When there is love, warmth, emotional support, tolerance, flexibility, openmindedness,and room for spiritual and emotional growth etc in the family home, the JW's don't look so good. If there is intolerance, no compromise, no spiritual or intellectual freedom of expressions, loud arguments, bad language, just think how good the Witnesses will look then.
I hope this, or some variation of it helps.
Life is a roller coaster. Get in, sit down, shut up and hang on!