One thing to remember if she IS having an affair, is that she no longer thinks like the person you married. That new person will have turned everything around in her head to blame it all on you, so she won't feel guilty. So that might explain the change.

And since you basically say the marriage is dead as is, why not just go and outwardly snoop? If she sees what you're doing, just say, "I've racked my brain to figure out why our whole lives turned upside down, I've changed everything I could possibly change on my end and it doesn't matter, so I've concluded that the only other possible reason for you hating me is that you're having an affair. So I'm working to find the evidence, so I can quit blaming myself."

What have you got to lose?

Oh, and man hating...I can tell you with 99.5% truthfulness that if I ever leave my husband, I will never look for another mate. I know many, many women like that. They spend their whole adult life taking care of a man, giving up who they are in life for the sake of the husband and kids...and finally just can't do it any more. They have to finally live with themselves as the most important person in their lives. Happens all the time.