Use it as motivation to further detach. Let go. Move forward with your life without her. And however you found out that the PA is ongoing, don't look there again (but save the info for your L).
Well said, sir. He does need to get everything he can - email/text/photo - for the lawyer.
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.
