I don't have any suggestions for his ED but I can give some advice on getting his diabetes under control. A few years ago, I was taking 5 pills and at least one shot a day. I am now completely medication free.
First of all, he must lose weight. Even losing 10% of his body weight will start to make a difference. Exercise is extremely helpful but the biggest thing is his diet. While every one is different, I discovered that in order to control my blood sugars I had to completely eliminate bread and potatoes, most pastas and rices. I severely limit starchy carbs and only eat small amounts of beans, brown rice, quinoa and oatmeal. I treat those items respectfully and only have them in small amounts. I eat mainly lean meats and proteins, lots and lots of non-starchy veggies, dairy and 2 servings of fruit/day.
Best of luck to him,