Simply end it, do the NC letter--and move on.
Make a list of all the things that are WRONG about the affair, and keep it somewhere where you can review it when you feel weak.
You don't say how long it's lasted. Mine lasted a long time, and by the time I ended it--there was no unrealistic fantasy. If yours hasn't lasted that long, it may be harder. However, mine lasted FOUR years, and I'm over it. I cried a lot at first, and I missed him at first too. HE'd been my emotional support for four years.
Think of this too. My marriage is over, I'm divorced after 21 years of marriage. Why? The affair. Ask yourself if you want to give up your long marriage, for this man with which you're having an A. Be very , very honest with yourself. What sort of man does this to his wife? (Granted, I cheated, and you cheated , too)
After exH and I separated, it took OM almost a YEAR to move out of his house, and relocate here. I could see right away what a huge mistake it all was. I also could tell I couldn't ever trust this man--found out later on in the R he'd cheated before. He refused to call his wife, in front of me, and check on the divorce status. To think I lost it all, for this type of man. What a fool I was. Dangerous infatuation, yes indeed.
One more thing--I've been coming and posting here since last September. I haven't been around here in almost two weeks, but I checked in last night and this morning. Your post caught my eye. Please, call it whatever you may-divine intervention--but PLEASE end the affair and come back to reality.
I so wish I'd found this site before it was too late for my marriage.
H_P