Well, it depends on so many factors, and we're not "one size fits all"...
That being said, most of us on this forum have our best success with controlling diabetes by eating LOW carb and with high fat and moderate protein.
I'm a 46 year old male and I eat as much as 10% of my calories from carbohydrate, and about 50-60% from fat and 30-40% from protein, give-or-take. Most people don't need as much protein as I do, unless they're doing serious weight training.
For 2000 kcal a day I'd recommend about 10% carbohydrate (about 50g), 70% fat (about 150g) and 20% protein (about 100g) for men as a place to START. It may need tweaking from there.
Most of the medical community and our governments are still advocating "low-fat" and with 50% calories from carbs, but that's just not the correct way to eat, especially for diabetics.
A Type 2 diabetic that gets 50% of their calories from carbs will QUICKLY become an insulin-dependent and very obese diabetic. Not a healthy one.
Everyone's diet is going to be different. I eat around 1800-2000 calories most days and a majority of those calories are from fats. I try to keep the carbs below 30 a day. That is what works for me. You need to find the right diet that gives him normal bg levels after meals. For me that is 10-15 carbs, 15-20 grams of protein and 20 -25 grams of fat. But your husband may be different.