Seeking expert counseling is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
Your grandson is being overly punished and has developed a great deal of anxiety about the use of his video games.
I don't think that video games are all that beneficial or helpful for the raising of children, but he has now become addicted to it and he craves it.
I believe that he should have a regular schedule, perhaps on the weekends and one night during the week. Withholding it has become a cruel punishment for him, even though it wasn't intended to be so.
Perhaps a better system of discipline could be devised by his father.
He is much too controlling and strict for a little 9 year old boy.
Your son is taking out his anger and frustration on his little boy, and this is almost abusive. He will injure your grandson's personality development if he keeps up with this.
You must somehow get through to him. You have the best chance because you are his mother.
I wish you great success.
If you would like to get back to me, please feel free. I am at your service.
Elliott Sewell, LPCC, NCC, CCMHC