Hello - you'll get loads of support and good expert advice here, so you won't need to wing it much longer.
I, too, am trying to lower my Hba, ideally out of pre-DB completely, but at least lower than my current borderline readings. Great that your husband has already reduced his reading significantly.
On the diet front, I've found it really helpful to get a blood glucose monitor (I just picked one off the Internet, but the experts here have a lot more experience on them than I do). I've 'played around' with it, ie, trying it out all over the place, against what I've eaten, what I'm about to eat, and when, and what exercise/activity I'm getting. It's trying to 'map out' what my glucose do around the day/night. They are simple to use once you get used to them (a bit fiddly!), and if you don't mind a drop of visible blood on your finger!
In terms of what to eat, the general idea is to shift away from carbs (both sugars and starches) and towards non-carbs. If you are trying to lose weight as well, then, although fat is considered 'ok' for DB, of course it pretty calorific, so you probably want to not go overboard on fats either! What I've found for myself is to focus on protein and fibre - meat and veg! (Unless you're veggie or vegan).
Getting used to having a meal with protein and veg, but no starch (ie, not potatoes/rice/bread/pasta) can be odd at first, but the protein and fibre really does 'fill you up' and you do get used to a non-starch meal.
Then there is the 'move more' therapy - aka exercise. Anything helps, but folk here will also explain the impact of the two kinds of exercise (cardio and weights) on our blood glucose levels.
All the very best on this 'new journey'.
