Hi Rosie, I've not been on for ages and have just caught up with this entire thread.
Fung is right, he is pretty much always right, but I also think you maybe confusing the real issue here.
Yes, it is very important to lower insulin, but it goes hand in hand with blood glucose. The only way a T2 can lower insulin production is by lowering blood glucose. That is, you can't achieve one without nailing the other as lower insulin levels is a direct consequence of lower blood sugar levels. The less glucose in the blood, the less insulin is needed, the more chance you have of lowering insulin resistance, restoring normal BG levels and controlling T2.
Diet is key, but is not a total fix without other lifestyle changes. I thought I was strong and fit, I have a manual job and am active on my feet for around 16hrs a day but then I tried Cardio exercise and suddenly realised how unfit I actually was. Aerobic fitness is key here if your husband is able and will make a massive difference.
Personally, I started cycling and 10 months ago struggled to do a couple of miles without collapsing but am now able to do 20 miles a day through the forest on my mountain bike, 6 days a week religiously.
I also stick to a one meal a day low carb, high fat diet and never cheat.
I really struggled to adapt at first with the diet for all the same reasons as your husband and spent many months feeling desperate and alone as well as constantly feeling weak ill. But I stuck to it and couldn't be happier, or fitter. All of my blood markers are within normal range and a recent stress test returned Vo2Max of 46, which puts me equivalent to a twenty something in aerobic fitness at the age of 53.
Oh and resting pulse at the start of my journey was 82 and is now 58 and Im at 21.5 bmi with 12% bodyfat after losing 2 stone of fat and muscle. The muscle can be gained back with lots of protein and strength training/work.
Life is now great, all thanks to this forum, the people on it who I listened to and learned from.
You and your husband are in great hands here, but a total commitment from him is critical to get the results he and you desire.
Good luck!