ETA The changes you're looking at aren't going to hurt him in the least. Gluten-free is a great move and couldn't possibly hurt. Also, less video games is always a good idea. I still say, go ahead and give it a try.
I know how distressing this can be. My nephew recently had some tics that needed to be addressed with medication. He's got some wonderful doctors and they are watching him closely. They have been trying the gluten free as well, and that along with the medication is helping a great deal.
I would definitely look around your area and check out some bakeries that promote gluten-free products. Many normal bakeries are offering some gluten-free choices as well, so your path may be eased that way.
Poor little guy. It's a difficult line to walk, telling him that the tics are a problem and still letting him know he's a normal kid. I know how much you want him to know he hasn't done anything wrong. If you present the gluten-free idea to him as if it were a journey the whole family is taking together, it would be a big help, I think.
Good luck. Keep us posted.