First off - welcome to mamapedia!! (even though you have told us this is a made up account).
Second off - I'm sorry - I gave up reading your book half-way through. This is a long-winded way to say - as your screen name states - you are IN A RUT.
What do I think is going on with you? You have regrets because you lived your life to please others instead of yourself. Okay. We've all had the "woulda, shoulda, coulda" moments. You are in a rut in your marriage. You STATE you are happily married - however - you are pining for a man you can't have. Face it.
This "man" (I'll use it loosely) is supposedly happily married and is, in essence, hitting on you. You, stating you are happily married, but if you face the fact - you aren't - are letting this guy play on your heart strings.
Wake up, Chicka!!! You willing to lose it ALL over some words and things you didn't do in the past?! If you were MEANT to be together - then by all means - go meet this "man"....get him out of your system....
Would I tell my husband I miss a friend? yes. In your situation - this guy isn't a friend. He was a romantic interest - even if you never met in person - and he's playing you. You don't have the "spark" you want and desire in your marriage - so this guy - who made your heart thump back in the day - is making it thump again...
Instead of wasting time on the "one that got away"? Invest all this energy into your marriage! Revive your marriage. Cut this cancer out of your life....if you don't cut him out - he will bring you and your family down with him. Do you really want that?