www.olganon.org. They have a weekly meeting in Bethesda. It's standard 12 step stuff. A heavily addicted gaming spouse probably will just scoff when confronted....they are just playing a "game". This is what can make it particularly self destructive. People spend money they don't have, get involved with their gaming friends and ignore their real lives....The dopamine high from gaming is hard to break from, as is having a secret social life that doesn't involve paying a sitter, making plans, driving, any real demands....
If the gamer wont get help, consult OLGA as well for online support. Consider seeing a therapist that specializes in addiction as well, (gaming specific specialists are uncommon)