In answer to your questions:
1. I don't think anyone can give you a reliable life expectancy estimate. It would depend upon the total clinical picture, the nature of his heart disease, and his liver disease, if any. However, other important determining factors are a) how well he controls his blood sugar, blood pressure, cholesterol and weight b) lifestyle factors such as exercise, diet, and smoking c) whether he address his sleep apnea and d) his psychological attitude / willingness to educate himself on his condition and take an active part in managing it.
2. If I'm not mistaken, any of the things you mentioned - seizure, passing out, or coma, could occur if he is not able to control his blood sugar. If you want to take an active part in managing his condition I would think you would want to know his blood sugar level every time it is measured, both day-to-day and A1C (three month average).
3. The chances he could require an amputation or become blind from diabetic retinopathy depends to a large extent on blood sugar control. Some people, sadly, do everything possible to exert such control and still wind up with these terrible conditions.
You can find much more comprehensive and detailed information at the web site of the American Diabetic Association at www.diabetes.org.
Educate yourself and your husband. There is a great deal to learn to manage diabetes well.
Please note that I am not a physician, either.
Good luck to you and your husband.
I'm not a doctor so you can take my reply as you like. The questions you post should be directed to your husbands attending physician(s). If he is dx with HCV he will need to see a Hepatologist, a liver disease specialist. Being "overweight and not active" is not good for his heart nor his diabetes. He needs to lose the weight, period. And do moderate exercise, such as walking daily to help lower his glucose. And most important, start eating healthier, a better nutrition goes a long way in maintaining life.