I am horified with the person I was leading up to and during my A.
I think this is important because your state of mind might have readied and primed you for:
I told the AP that I loved her.
When you are feeling depressed and needy, this understanding EAP can seem magical. I think it's clear you were caught up in the EA:
Even before our A, we were close.
I don't know the answer, but why were you moving towards your BW SIL, instead of your wife?
I think I was being honest --i.e., I wasn't just saying what she wanted to hear.
JMO:
I believe we are capable of feeling healthy and
unhealthy love. Affair love is not healthy and is flawed in so many ways. Saying ILY under those circumstances and dark choices is never healthy love.
We love close, good, friends, not to be confused
with love we should have for our S/SO. During
your A, you never considered that your AP was not a friend in the true sense of the word. Saying ILY strengthened a false bond and made the A and the AP more important and significant.
None of this may apply to you. I believe it's only a small part of what happened in WSO's A. The ILY's served a purpose and made the A more acceptable and passionate. He wanted to think he loved AP because it made him feel better about what he was doing and destroying.