Quote: Maybe it's the medication I'm taking for the ADD (I've never been able to stay on top of an argument with her like I have been lately...before, I would get flustered and befuddled...none of that now).
I think you nailed it right there. Whether it's due to the medication, I have no idea. But it's obvious that what has changed is YOU. Assuming that your accounts of your conversations are true and accurate, you have done a complete 180 from where you were a year or more ago.
She used to be able to run right over you. She's used to that. She COUNTS on it. Now she can't do it anymore, and you've got her flustered. You changed yourself, and so the relationship has to change. Where have I read that before?
In fact it seems to be working so well for you, you're inspiring me to try it out myself....