Ah yes, personal hygiene with 11 yr old boys. He is not to the personal awareness yet, but it will come, in the meantime, it is all work for Mom. You need to limit the game time and only let him play when he has his shower, teeth brushed, etc. Put up a list in the bathroom if you like, with a dry erace board and a marker so that he can check it off as he goes through the list. Check his breath to make sure that he brush (spot check if you want). Get him some cool men's shampoo, etc. They are so stuck between the child and next stage, you almost need to handle them on a preschooler level.
As for the main problem, that is really unusual. You need to have a talk with him... again... and tell him about the health risks. It really isn't good to ignore what your body is telling you. I like the idea of him earning game time. I would tie it in with the soiling situation. If you have an idea of when he does go, then you can remind him at about that time every day. It isn't easy with a preteen, but get him more exercise, it will help in all areas.
With mine, he wasn't allowed to play video games or watch tv, etc, until his homework was done, but he could play outside with his friends as long as he wanted. I was hoping that this would encourage outside play until dinner time when the neighborhood kids had to go in to eat, and then he was required to do homework before going back out or playing games. It seemed to work for me, he hated homework so he would skatboard for 2 hours in front of our house and he got more exercise and it helped relax his brain so he could concentrate on homework.
Good luck... I am afraid that these are normal problems for many preteen boys. If you can't correct it with coercion etc, then it may be a medical problem, but it doesn't sound like to me, but I am no expert.