How awful for you WM. I have a friend who is going through a similar phase with her ds and sought professional advice. Their advice was to echo SS's words. But they also advised that to avoid violence, you need to diffuse violent/heated arguments and be very very calm as the parent.
Have you read 1,2,3 Magic? Whtever the problem, it advises always staying calm, and stating "That's one" "That's two" "That's three" before always always following up with a consequence. It's supposed to work for under 12s - and works with my two, when I remember to stay calm. (You are supposed to do "Time out" as the 'punishment' according to this book, but we have adapted it to a variety of punishments, as long as we have got to three.)
I know that computer games are particularly hard as they are soooo addictive, and designed to make you want to play for just 5 minutes more. They also get my dss wound up like nothing else except Coke (Cola that is!) I have adapted the rule with mine that the oldest is allowed an hour a day on it, but then allowed an extra 5 minutes if necessary with me watching, to finish off a level. It's worth discussing with your ds, when this is all over, how long is really reasonable for him to be on the game and what happens if/when you need him to finish sooner.
HTH a little. I'm sure someone will come along with more advice soon. (I have a copy of 1,2,3 which you are welcome to borrow if you want to CAT me)