SM, the contextual difference is huge, between being in a convo with your W and stating what you want and mean vs seeking her out specifically to do so.
As much as you want to go to her and dump on her what you feel about her choices and your goals, that remains a sitch of you thinking that words will change the sitch. They just won't. Even if it SEEMS like words change a sitch, it may be very likely that the words simply validate changes that have already occurred and therefore follow a choice that has already been made.
ie. If you go to your W and say that you do not like that your W is having R with OM and that she needs to make a choice between you and OM. What ever she does, she had already chosen and your words weren't the catalyst to the choice, they would simply validate the choice she already made.
So all I'm really saying is, you can choose to stop being a "nice guy" and doing that is in the context of now and into the future. And that is FOR YOU. You would not specifically be doing that in order to "fix" the M.
You need to continue to move on with your life regardless of the outcome of your M. Live your new behaviours regardless of the sitch and when there is comm between you and your W, maintain that behaviour. It needs to be a habit.
And once it's a habit, you are likely to see what the changes in the sitch are, decide whether they are good or bad (or appear to make no difference) and then course correct if necessary.