Do you think they didn't have these conversations when they married?  Why should he trust a single thing she says? 

OP thought he was in a happy marriage.  He happily took care of his wife in her darkest hour.

Meanwhile, SHE was having at least an emotional affair, while planning to divorce him.  ONLY when the other dirtbag threw her out like yesterday's trash, and she had to settle for being cared for by the guy she had neither any respect for nor desire to be with, did she stay with her poor hubby. 

Read these two paragraphs to yourself.  The second person does NOT deserve the first.   The first deserves much better than the second.  Being blindly optimistic does him zero favors. 

He has the chance to stay over with someone who won't treat him like absolute garbage.  Why advise him against that?