An ADHD partner dealing with my partner's anger

Hi there, I am 40-something male with inattentive ADHD. I have suspected my whole life that I have it but was only diagnosed about a year ago. That said, my non-ADHD wife and I (together 18 years, married 14) have long struggled greatly with issues related to my ADHD. The elements described in the ADHD Effect in Marriage and Couples Guide to Thriving with ADHD books resonate very deeply for me---the parent-child paradigm, symptom-response-response, indecisiveness, fighting, sexual issues, etc.--places where my unstructured brain and fear of doing the wrong thing and my wife's yearning for order and structure and reliability collide. 

I could go in more detail there but the real issue is that all of this leads to extreme anger from my wife. She gets so upset that I am not able to hold up my end of the bargain, that I'm not able to make and then sustain changes, that I leave so many of the decisions to her, etc. etc. I hear her anger as admonitions (which let's face it, they are), I cannot handle her anger (some of the stuff is really mean), and it causes me to snap back, and then the cycle deepens until we're all worn out. I would render a guess that this happens about once a month. 

Most recently, we had a really good stretch, as I'm trying to get a handle on my ADHD (although for a variety of reasons ADHD medicine hasn't been able to work yet, so it's going slow) and she's been extraordinarily patient with it. Then yesterday she got upset because I misunderstood something. Then I forgot something. And I did some regressive things like wait for her approval on stuff. Then we had a failed attempt at sex (where all this stuff came into play), and that exacerbated both of our feelings.  

I am in need for any advice on how I can adequately deal with her anger. I know that she is angry and honest to God I understand why as well. I also totally know that snapping back at her, or getting defensive, or completely shutting down, are very unhelpful ways to deal with it. But when she says something mean to me because of how deeply angry she is, I can only take so much. How do I take care of myself while also giving her the room to be angry? How do I do that without completely shutting down, and while continuing to be taking care of (and being kind to) myself? Thank you for any thoughts you might have.