Continuing in the very direct vein, it sounds like your conversations with your W are collective monologues with neither of you listening to the other, a common feature of a couple with a relationship seemingly heading in the wrong direction.
A mediator is a fine idea as they will keep things level and ensure neither of you over imposes themselves on the conversation.
What I'd suggest you do before you get into one of the sessions, or have another conversation with your wife, is to study on how to listen and really hear what your wife is saying to you. Stop thinking about what you are going to say next and focus on every word she is saying. Also look further into Validation on this forum. It could be that by simply using your ears twice as much as your mouth you might find your wife opening up and if you are smart will use the clues she gives you to get your R back on track.
Finally, when was the last time you read the DR book? From what you have said above, it would seem that the answer is "too long ago" and you need to remedy that pronto!
- Nobody has ever learnt anything important from happiness and success; problems make us grow - Consult your plan, not your feelings - If you haven't set goals, how can you expect to achieve anything?