If he has a severe gaming actual addiction then he can't control it and it needs to be taken from him.
So you remove Internet, remove everything from his room til you find the console and games and you get rid of them.
Then you contact the police if he assaults you.
All of these NEED to be done to keep him safe and stop his addiction.
If he's not addicted then you are just going to have endless battles about control, minimising, managing etc which is very wearing.
I say this because it might help you to be clear that if he is addicted then the only option is to be stopped playing, anything else you do is just facilitating addiction. If your child was addicted to anything else like alcohol or drugs you would remove it from the house.
Gaming addiction is the same, it's just no one wants to hear it.
If you don't think or don't want to think he's addicted then that's fine but my advice will be different.
{{{{{hugs}}}} even though we don't do many on Mumsnet. What you're about to do if he's addicted will be hard in one sense but very easy in another. If he's addicted you will save his life and the life of others. But you have to and absolutely have to, stick to it.
Once you've removed it all and once you've gone through the initial kicking off it will get much easier. You are going to need to call the police if he assaults you, for a myriad of reasons . But he has to take the consequences of that, a criminal record is better than losing your life to gaming.
I can hear how much you've tried, I bet you've tried everything. But if you're sure he's addicted there is only one way to go with something so serious on an adolescent brain.