In sickness and in health eh, op.
I should imagine your imagination is running riot. Could it be the time to just ask him what exactly is between them, friendship or more.
He probably won't tell you the truth but you may see his reaction.
Would he stop seeing her, or working with her ?
What you have seen "I dreamt of you last night" is heady stuff, enough for you to assume an emotional affair, would he accept that is what it is.
It's so difficult with a long marriage, it takes time to unravel information and feelings whether you stay together or not.
One thing is for sure, he has hurt you, when you needed him, he was emotionally present for someone else, that needs to stop, it's up to him to do that willingly.
I can tell you he's fucked up, similar situation to mine, all I can say is after a number of years his friendship ended but so did his marriage to me.
Now he has no one, feels awfully sorry for himself about destroying 35 years of support and love and knows there is no way of repairing or turning back time. I think he honestly thought I'd forgive anything, so sure was he of my love for him but he hadn't banked on my hate for him for what he did..... A test too great.
Nobody wins in these situations, family, friends, colleagues it's very difficult showing them how much they stand to loose, but he's on a path to destruction and the company they keep don't care either.
You have some difficult choices to make, choices that no one after so long should ever have to make, I hope he makes the right choices too.
Take care
