ADHD husband overwhelmed by the programme

We have hit a wall. My AHDH husband and I (non ADHD) downloaded the online seminar and we have both found it an amazingly positive experience. It has helped both of us understand each other and our ADHD marriage a lot better, and start working on change. 

We listened to all the sessions and did all the homework. We were unable to keep the pace of one session a week, mostly because his ADD symptoms made it difficult for him to follow through, get the homework done, listen to the audio chapter etc. So we spaced it out more, and we got through it all in the end. I learned to adjust my expectations around how long it took for him to get things done, and realised it was fine to take it slower. We took 5 months to do the whole programme. 

We started weekly chore meetings, and he has been taking on a lot more chores and really sharing the load. For the first time I felt less alone, and I felt a shared responsibility in our marriage for things like financial decisions, vacation planning etc. 

The specific challenge we are facing now is this:

Recently, we got to the Intentional Relationship planning. We each made an action plan. I have been implementing mine for a month now. He started implementing his two weeks ago for a few days, then he stopped. He then became extremely distracted, uncommunicative, skipped chores and skipped a chore meeting. 

He says he felt overwhelmed by all the stuff he has to do. The chores, plus the stuff on his action plan, which is mainly around exercise and things to increase his energy level. He says his symptoms went through the roof, and he couldn't do anything about it. Meanwhile, I have felt very alone, back making decisions and doing chores on my own, and feeling like I will never know when he is going to check out and leave me to manage everything alone while he has these periods. 

I am very concerned, because he wasn't actually doing that much. I mean less than a normal amount of chores of any non ADHD person, with longer time in which to do them, and still with me picking up the slack. His plan only involved a couple of hours exercise a week, plus some time on brain training online. 

What do we do now? Is this as good as it will ever get? That's not enough for me. I am kind of devastated right now, because we were doing so well but now I feel like we have hit a wall. I don't see a huge improvement in his management of ADHD symptoms, and they are still wreaking occasional havoc. 

Anyone experiencing this kind of wall? And ideas please?