Your boy is bored and the computer games are his way of dealing with it,he does need some Physical activities as this will help him, do not take thePC games away but lesson them, fill some time with outside activities and sports , you say you have a work load ,is there someone can help you, any friend can come by and play basket ball or soccer if there is a dad around get him involved also,dont worry about his messiness it is him to has to live in his room,teens do that, focus on his positive side , get him busy.
I think you should'nt give into the behavior. You have to stand your ground or else he will soon feel that he is in control of you. People can make excuses for the behavior, but he learns that his behavior is NOT acceptable he will turn out a much happier guy in the long run... it might be battle for the time being trying to get him to cooperate with you but you have to look at the bigger picture... if you blame his behavior on him being "bored" and give in imagine him 10 years from now what his behavior will be... Set a firm and good example of how you would want him to raise his children one day.
I think you do need to set some rules and limit the computer time. You are allowed to have rules in your home as long as he is living there. You need to be firm. Sit him down and tell him that the disrespect will no longer be tolerated and if he destroys his room, shouts, acts mean or disrespectful that he will be grounded and the computer, cell phone, etc., will be taken away until you decide. He will balk at first if he's not used to a lot of rules. Expect that but stay firm and consistent. Kids need boundaries.
I agree that he needs outside activities to be well rounded and healthy. Sitting in front of a computer or video games all the time is not healthy for a child or an adult. Get him involved in some other activities and keep the computer out where you can see it. The computer usage should be a privilege just like driving or anything else that will come up. It's not a right, it's a privilege. Too many kids today think it's their right to have all these things. Not at all. All we parents have to do is provide a warm shelter, food, clothing and schooling. All the rest is privileges and they need to understand that. If he doesn't act right, he doesn't get these privileges. It's as simple as that. You are the parent, he is the child. Remember that.