Video game led to emotional affair

We bought an iPad for our son, who is delayed and has low vision. My husband discovered some of the game apps and one in particular, a Renaissance-ish war game, caught his fancy. A bump in our relationship has ALWAYS been video games. He gets so over-involved in them, he'll waste an entire day playing pretend war. The iPad being portable just made things worse. He checked his game obsessively. Tuesday night he was out and the iPad had a notification from this game while I was doing vision therapy with my son. After therapy was done I turnd on the game to get rid of the notification - and was shocked. The game has a messaging feature and I read 37 pages of emails between my husband and "LadyVixen." The ones that hurt the most were when he called her "honey" and "my little secret" and when he was obviously chatting with her when our two boys were around. I am so angry, hurt, embarrassed, sad, insulted, used (he's been unemployed for he last year), manipulated, lied to and stupid. I was a history minor in college, so that this person was in a idealized Renaissance game insults my intelligence. I feel like I can't talk to anyone about it because it's so ridiculous and stupid.