Boy, can I relate to that! I was 350 and diabetic type II. I also have COPD, Emphysema and a few other hard to spell problems.
You can not make him do anything. You are not responsible for his actions (or lack of action). Go to a good dietitian and get about 10 or fifteen meal recipes of things he likes. They are available. The trick with diabetes type II is the consistency with carbs. Spread them out over the day, never over do all in one meal. get a good low carb chart and stick to about 200-250 grams a day and see how it goes. Adjust as needed per HIS doctor’s advice.
You can not make his change his eating lifestyle. He has to want to do it for you, for his family, but most of all for HIMSELF!