He did have trouble understanding it. He had to process a lot of the 'information' for a long time to get to the point of acceptance. You don't have to understand it to accept it and he did eventually realize that.
What helped (for lack of a better word) him is that we are madhatters, and he was the WH many years ago. I think that because he had been there in his head at one point, he understood the insanity. I often joked to myself that I was grateful that he had cheated on me because that helped him get to a place of understanding my despicable behavior.
In your situation that's not the case so...what you can do is keep being consistent in your actions, be 100% honest at all times with everything, and be patient. Commit to being the person you want to be and know you can be and act accordingly. It is a long process but definitely possible to get to a better place.