Her Opportunity Cost
I thought about it some more:
Ever read Nitszche?
Its called "inter pares" AMONG EQUALS
People generally associate with people like themselves. You are not on her level. This is the fundamental problem and now she wants somebody on her level and is too nice to dump you. Poor girl.
You said your wife is REALLY hot. IMO, she HAD a self-esteem problem with guys, i.e. was timid and married you because you were nice. You problably played used the "friend" seduction method ugly losers use.
So now with time she KNOWS she can do better and wants better but again, is too shy, if she wasn't she would have a better man, to leave you, so she does the nice thing, the easier thing, the pussier thing, and asks for a MMF what she really wants is a inter pares man.
I personally think you fucked up her life. You have 2 kids. Nice going
I would be a man and let her go. Talk with her. Deep down inside you probably know that she is yearning to look for someone else but is too shy to do it. If you really care about her, give her permission to search around, date, f, etc.........until she finds the man she is looking for an inter paras man and securtiy.
In the futrue, work on your shit and do not try to manipulate women by becoming a friend to a super hot girl with self esteem problems, and working your way in, and catching the hot babe.
In the long, you hurt her life. In the Investment world, its call "Opportunity Cost." She gave up someone else for you.
Seduce a girl first. If you cannot seduce her, find another one you can seduce (i.e. turn on and fulfill her dreams). IMO, that girl will not be as hot as your wife.