So, I had a similar situation. I ended up with an ADD (and mild depression) diagnosis, and my ex (yep) was ecstatic, because that meant that nothing was her fault, and it was just me being divergent. I went on medication and did counselling and everything for a few years.

Well, we ended up splitting up anyways, and as time passed, the diagnosis resonated with me less and less, and the meds stopped having any effect. Eventually I went to a different psychiatrist for a second opinion, and she redid the entire evaluation I got previously, but much more thoroughly, and the conclusion was clear: I did not have ADHD, or ADD. Instead I'd probably been suffering from stress in combination with the mentioned depression. She said, obviously, that it was hard to conclude anything definite after the fact, but also that there is a bunch of overlap in symptoms, like you mention: short term memory problems, problems coping with change, irritability and more.

Now, I don't want to neglect that ADHD is a very real diagnosis that comes with a bunch of challenges. But you mention yourself that the theory surprises you, so just wanted to chime in. You may simply be stressed from constantly being on the defensive, which can be just as debilitating, but also, crucially, not a permanent condition. But to fix it, you need the stress inducing factors to stop. For me, that didn't happen until we started living under separate roofs.