Same position except I played the PI myself, found the password and read the detailed sex talk, declarations of love, descriptions of how he had never loved me really but I pressured him into having children and marrying, and how shit I was in bed and as a person.
I know it's him desperately deluding himself, finding a reason why it was fair enough for him to have a year-long affair, take her to sex hotels, on holidays etc. But even though the stories about me and our life are in large part jaw-dropping fiction, I know that if he tells his girlfriend this, he'll tell his family and maybe even the kids the same story, and I won't be able to defend myself. I'll just be working or walking along when a line from his emails pops into my head and it feels like someone kicked me in the stomach.
Part of me is relieved to have proof it is not just all about me, as he led me to believe. But part of me says that maybe some of it is true, and I am shit in bed without knowing it, and an evil narcissist as his girlfriend (who has admittedly never met me) says.
In fact I don't even have proof that it wasn't mostly my fault, as he still says (in a weaselly, indirect way) that he was forced into it by my bad behaviour, and couldn't help it.
So it hasn't been all helpful.