Yep, the ONS was a pretty low act, I see why you struggle for forgiveness there especially with the repercussions.
It could have been there was something he was missing. I'm sure you have probably, like we all have, done some pretty thorough self-examination. Or it could have just happened, a snap bad decision. There is no excuse though.
My H does the same thing of, if you don't voice it, it isn't happening. Infuriating isn't it! He lies by omission. I had to find out about ow on Facebook and even when I confronted him by email he still never admitted it. From what I have read of your thread you are doing so well in yourself.
On reflection from what you have said about telling your H perhaps you are right. My H has reacted much better from when I told him it was ok and I wasn't angry. I had to wait till he was able to 'hear' it though and judge when that time would be. If I had said it any sooner or in another context it wouldn't have had the same affect.
My DB coach also said that about H and ow. It was something like the ow is on his level at the moment and the bar is pretty low. He feels he doesn't deserve better.
25yearsmlc says 'be the woman only a fool would leave'. This is what I am trying to be. I see this as a win win situation. My H is still deeply involved with ow but I see there are chinks of light. I see lots of light in your situation and I think you are going to totally make the most of this counselling oppertunity. Keep up your PMA!