Your MC wants you to focus on your M, but her prohibition on telling oBS has backfired - you think about outing the A a lot. In your case, telling would have allowed you to focus more on your M.
I don't get the MC. I absolutely agree that ow is not your problem, and the less energy you focus on the ow, the better.
But telling isn't at all about hurting ow. It's all about protecting the oBS, and once it's done, it's done.
You've expended some serious energy in finding oBS, more than many of us would. It sounds like you haven't found him for sure, though. You could just drop this, and give yourself a pat on the back. Or you could do some more digging, and, if you find him, offer your info.
Either way is OK. But it sounds like you can't heal unless you do one or the other, so choose and celebrate what you've done.