Sorry to hear that you're feeling down....but don't get down too much on yourself. We all go through the cyclical feelings that you are experiencing, heck its even natural. The point is, in the overall grand scheme of things, you are doing wonderful. Getting bogged down trying to analyze what that WAS' are saying can only lead to further frustration and confusion. I go through the same things, in fact on Monday, my W gave me a nice card with some written thoughts in it. Very nice...but my over analytical mind kicks in and focuses on several key phrases and the fact that its not an "I love you" card (altough she does say it IN the card) but a thank you card. Okay, point is, I look at that and know its not what I expected of the "old" her, but it is something. It just also tells me that while things are improving, they are not just there yet. Patience.
So don't get too analytical about the cryptic stuff, it will only drive you insane! Also, recognize that while your SO hasn't obviously shut the OW out of his life, it is still progress when he acknowledges that there is trouble in paradise. Its a babystep in the right direction.
Look at yourself in the mirror and affirm that you a good, decent person deserving of love and respect. Find that PMA!
"Achieve success, but without vanity; Achieve success, but without aggression; Achieve success, but without gain; Achieve success, but without force." Lao Tzu