(((Scubadoo))) I'm so sorry you are here, and I'm sorry your WH is so back and forth. I know that is a hard place to be it -- hoping and feeling like you might have turned a corner, only to find your one step forward has come with two steps back.
It sounds like you've found a good MC. They aren't all good - and sometimes condone rug sweeping, so as you try to see if R is possible, it is great that you've found a good ally in that.
Please post, and post some more. That's what SI is for. All of us have been there - and many of us under the same circumstances (SI is one of our only places to talk).
I got the say "brainwashing" speech from my ExWH. It is simply deflection -- not wanting you to take your power back -- not wanting you to be strong enough to create your boundaries and keep them.
I truly thing SI is the best thing that can happen to anyone -- whether they D or R -- the wealth of experience for BTDT literally saved my sanity.
I do think your MC is right -- although, it's not that I think you should let go of your anger at OW. Its justified. At the same time, it IS an easy trap to fall into - letting the OW bear the brunt of our anger -- and letting if overshadow the responsibility of the WS. In the end, if anger at OW takes up too much of your headspace, that's really just hurting you. I spent many a week (months??) dreaming about outing OW to everyone in the universe. And honestly, I'm not (personally) in the camp that preaches restraint in these areas, BUT -- it was just a lot of wasted time for me.
I finally realized that there was no justice I could dispense. There was no action I could ever take that would make us "even". There was no pain I could inflict that would make her feel what I was feeling, and get her to feel real remorse. That was just out of my control. That helped me clear some of that from my headspace. I still hate OW, but she doesn't live in my head anymore (or often at least since I still have to deal with her. But I let go of the obsessing for ME, not her.
Anyway, I just wanted to emphasize that there is never too much on SI. Post every day - about everything that has happened if it helps you -- no one will ever tell you it’s "too much"