Well, Tech, it looks like you have a good start going towards a polyamorous relationship to be included in your life. It truly helps that you get along so well with the other man. It seems you would genuinely like him regardless of if he were involved with your wife.
I come from much the same background as you do just of a longer duration. We were married 20 years when we started swinging and 22 when we met Tech and Kitten. We are at 25 years now married.
You mentioned something in your post that I thought was very insightful. It took me a long time to realize that was one of the things I had been feeling. You are in mourning. I totally understand that. Even if your new path is something you are embracing, I think it is natural to feel the mourning process.
Good luck to you all and welcome to the forum!