I agree that there are times when a child needs discipline, but it sounds like things just aren't working out in your home. Our boys play their DS's and would continue until the cows come home if we let them. Our oldest (8yr old) has had it taken away for 1 month for making a bad choice. He is due to get it back this Saturday. All week long he has been asking and nagging about getting it back early, but I just stick to my guns and tell him "no". The rule in our home is who ever takes the toy away is the one who rewards it back. (I'm lucky here. Daddy took it away.) I agree with your husband about not letting him take it to school. I feel that the games are a distraction and a magnet to others.
However, I disagree with your husband about the extra homework. That is just absurd. Your son could find something else to do like read a book, magazine or even comic. He could draw, write a journal or find out if the supervising teacher has something to do that would help them out like correcting papers, sorting, making copies, etc.
In my opinion you are making things worse by being more lenient with your son. He must feel confused. Each parent is from one extreme to the other. You know the good/evil thing.
Family counseling sounds like what your family needs. Your husband may protest, but if he cares about the family, he will go. There may even be something that is bothering your husband that has nothing to do with your son yet he takes it out on him. Men who really care and love their families will go to counseling. Those who protest have some deep personal issues that they are afraid to reveal, even to those they love. (Skeletons in the closet like a childhood trauma)
Talk with someone before you approach your husband and get help for your family.