He sounds depressed. Diabetes is depressing without constantly being told your body will fail.
After nearly 15 years of type 1 diabetes (where I been very lucky in having okish control), the best things I found that helped me control my diabetes was a doctor. He is now retired. But he showed emphaty and told me it was OK, to get random bumps. I wasn't a pancreas and I would never be one.
I just needed to do things to the best of my ability with the information I had then.
He then said how can I help you. After few suggestions I had my normal blood test and it turned out I developed hypothyroidism.
I took the thyroxine and I was then able to reduce insulin and get in control of my diabetes again.
I don't know how to encourage your dh. I know sometimes my mood goes down and I start thinking what is the point in trying to be good, when things out of your control influences blood sugar. For example, infections (first covid infection I had to reduce my insulin drastically (I did all and my second covid infection I had to increase drastically) and life stressor.
One thing that increases my insulin sensitivity is early morning walks. If I walk or exercise 30min before or after breakfast, the rest of the day I have to reduce my basal rate. Well I have to do it two days straight for the sensitivity to change.
Would he be interested in morning gym? Or walks?
I now view my diabetes like a hyperactive young toddler, who you need to keep a constant eye on. Consistency is key, in keeping them safe but expect the unexpected.