I am really having difficulty knowing how to act without being seen as controlling.
Don't disappear from the R in an attempt to be "nice" and give her lots of room. It's okay to act like you care what happens to the relationship. In fact, it's really important that you be present and visible, kwim? Has she given you some indication that she sees you as controlling? Most women (who were still emotionally invested in the marriage) IMHO would think it was sweet that their H wanted them to wear his ring.
FWIW when I was married the first time, I had an affair. (Long time ago, I've been divorced over 30 years now, and my first H has been happily remarried over 30 years.) When my husband asked me, I told the truth. Often-- maybe even most of the time--people do lie, but they can welcome the opportunity to finally get it out in the open, especially if they are planning on leaving. Someone who is planning on continuing an affair and NOT leaving is more likely to want to keep it a secret. I wouldn't assume she would lie about it. She might. She might not.
