Great insightful self-examination. I also can see myself in it--especially allowing one little comment by AH to control and overwhelm me so much! Why do we let that happen? I remember watching AH saying similarly hurtful things to my MIL, and she'd confront him, yell a little and then pouf! It was gone! Not that I want to confront by yelling, but why can't I get to the pouf! stage faster?
I think the awareness, and the pain of this experience with your son will open up your ability to respond, not react, to your AH. If you can step back and watch your emotions, watch the spiral as it occurs, pay attention to those feelings, know what's happening, and identify a better way to move forward you'll start changing that legacy for your son.
Thanks for the post.