My wife and I like the approach of the Kirk, on his website called Celebrate Calm. He empowers both parents and children, and he focuses on teaching all parties responsibility for themselves. It may not be easy, but we see that 'the failing way' is how we got here with our oldest son, so we have nothing to lose. We love his approach, actually.
May you and your wife be zocheh to say "we" this and "we" that, a lot more. Difficulty with our son was one of the strongest catalysts that brought my wife and I together. We didn't even realize how much we were on different pages! We were advised to huddle about every little response to our son so we'd never give him divergent and confusing messages - or a way to play one of us against the other. These little kiddies become very manipulative from a young age, and carry it into their teens and beyond.
Love you very much, fellow struggling parent!