Oh, honey, I know.
My WH is ready to throw it all away for a woman who, while attractive, can't tell the truth to save her life and clearly has no compunction about breaking up a marriage of 10 years and three kids.
Like someone told me in another thread, it's like it's not even him – it's like an alien wearing the body of your partner.
I so desperately wish there was someway we could just force them to open their eyes and see what they were doing. Keep doing the 180, though. While I don't know if it had much of an effect on my WH, it's certainly given me a lot more confidence and a better attitude. Are there any local activities you can get involved in? Sports? Book clubs?