I think you’re right. He can create a narrative around the adultery that makes it your fault whereas unreasonable is unreasonable and it is harder to defend in his own head. A part of me wishes that our need to protect our own ego wasn’t so strong, but it is what it is. I am guilty, though not to the same degree, of this as your STBXH.
Self reflection is not for the timid. And your H always had a bit of a coward to him - why else live two lives.
It doesn’t matter now.
Have you looked at properties? I know how hard it was/is for you to think of losing the house (all those hopes and dreams, right) but I think (hope) that once we both get our heads around it we will see they are just houses. It is what we bring to them that makes it our home. I heard, and am no expert, that it may be better to sell and rent for a bit. The market will drop again soon and we will be in better positions. Just a thought. Not sure about up north but where I live the market is very very over inflated.