First of all, throw the word "diet" out of your vocabulary. "Diets" are temporary, and provide temporary results.
No one, including me, likes to admit this, but you lose weight when you burn more calories than you consume. (Caveats given to certain medications and medical conditions.) The concept is simple, but the road to getting there can be tough.
The minute you make certain foods "forbidden" and start obsessing about calories and portions size, the more you think about food and hunger. If he's hungry all the time, then he needs to eat frequently, throughout the day. Some people are "grazers", and it's actually quite healthy to eat a little something every 2-3 hours. It keeps your blood sugar level constant, and it prevents you from becoming ravenous and thus overeating. Snacks with fiber, protein, and "good" fats make you feel full: meat, cheese, nuts, hard boiled eggs, protein bars and drinks, whole grains.
Does your husband seem to be able to tell when he is truly "full"? Did he grow up in a household where everyone had to clean their plate, no matter what? It can be hard to "unlearn" lifelong bad habits.
He can't eat junk when it's not in the house, and he can't eat half a chicken if only 2 chicken breasts have been cooked. It's all about lifestyle changes and the WHOLE family making them. Help him stock the house with healthy snacks and food choices that he actually likes. If he doesn't like pretzels, don't buy him pretzels hoping he'll eat them.
I'd rather poke my own eyes out than exercise for the sake of exercising. If you're husband is the same way, find natural ways for him to increase his activity. Maybe it starts out as simple as one day a week, he parks a couple of blocks from work and walks in. Maybe as a family, you go for an afternoon stroll on Sundays. Stress the time spent together, versus your husband getting his exercise.
Also, I would not make the wedding the main focus of your husband losing weight. If he doesn't lose the weight by then, he may feel like a failure, and you may be angry or diappointed. Also, the wedding will come and go. It's just one day. If he wants to lose weight, he needs to do it for more reasons than that.
And that's my last point. HE needs to want to lose the weight. I agree with another poster, YOU sound very focused on this, and if you were my spouse, my feelings would probably be hurt and I'd feel under a lot of pressure. I don't see anything in your post about your husband actually wanting to lose weight. And you mention he needs to lose 50 lbs. He may not be able to, especially if he has been overweight most or all of his life. Some of us just "are". Maybe he can only realistically lose and keep off 20 lbs.