So, I am just supposed to wait for him to bring up conversations about the R? How will I know when it is ok to start being more engaged/pursuing on my end? I assume I am to wait until he takes more initiative than me.
That is correct. Men like to pursue, so use that to your advantage. We tend to value most (all humans do, actually) that which is somewhat difficult to obtain. I know it seems counter-intuitive, but it's a core part of DBing. It's really nothing more than basic "push-pull" human dynamics between men and women.
Did you really reject him sexually during the marriage, or is he just re-writing marital history?