How do I expose the affair

[Allen A]

If you try some of the dialog above and he tries to tell you she's just a friend IGNORE it and stick to the script.

You need to practice protesting without him baiting you into a back and forth fact-refuting banter.

Tell him she's attacking your home.

He will deny the affair.
He will tell you she's a friend.
He will tell you she's helping.

IGNORE it. Repeat "she's attacking your home" and then LEAVE...

Once you have said it once or twice he has heard it enough and you don't WANT to repeat it.

Just enough to get the protest in his head and then get OUT of there. If you protest and THEN an argument ensues the protest won't have any impact, he will just remember the argument after it and feel hopeless.