Uhm, actually, according to JW standards, maybe he would be cheating on his wife if he was masturbating?
Depends.
Officially, the reason that masturbation is wrong is because it involves sexual fantasizing, which is a violation of Mt 5:28. But if a married person masturbates, and thinks only about their mate, then there is technically nothing wrong with it, by published dubbie standards.
If they fantasize about someone other than their mate, OTOH, then they are committing adultery in their heart.