Complex, after you read DB or DR, pick up the book "Boundaries," by Townsend & Townsend. It's widely considered THE definitive book on the subject, and I think it will help you.
btw, what your wife is telling you about talking to family or OM is purely SCRIPT -- they ALL say that. While exposure is against DB teaching, I certainly wouldn't LIE to anyone about what she's doing, and I would also tell her "I have decided that I will no longer lie to cover up your affair," even if you don't end up telling a soul.
Any time she threatens divorce, calmly tell her "Yes, I've heard you, multiple times. Do what you feel you need to do, but please stop talking about it as it's immature and disrespectful and I don't want to hear it."
