I agree with Tryingtoholdon that communication is the most important part of a marriage. She started the cold war, but you have continued it. It's not easy to break down the walls. I guarantee you that in Retrouvaille you will get beyond the walls. I'd say go back to where you started, offer to go to Retrouvaille and work on the marriage. I know FIL will back you up.
You could open communication with a heartfelt non-condemning letter. But the distance between the two of you is enormous. It will take an entire weekend of focus to open the doors. So I would say try a little communication on your own, but go to the professionals to do the bulk of the work. Marriage repair is not a do-it-youself project.
