This struck me, too. That you even compare her weight then to now, a couple of decades and five children later, is sad. Face it, she is never going to be 120 pounds again. And you’re never going to look as good as you did on your wedding day, either.
And, “healing separation”? For you or for her to heal? My goodness, if I thought my fiance would ever suggest such a thing due to my weight gain over 20 years I wouldn’t marry him to begin with.
I think there is a right and a wrong way to approach this, and I have to say I think you are taking the wrong one. It is one thing to say “My wife is obese, I’m worried about her, and it affects my attraction to her and our relationship. How can I help her?” This isn’t unreasonable. It allows for the approach that you are in this together, that a lot of things have happened over the years, that you love her and want to grow old with her.
What you are saying though, is “My wife is obese and unattractive, it’s her own fault, and she is ‘unrepentant’, so how can I fix her? And if I can’t, I’m separating from her.” Blaming her and threatening separation doesn’t fix anything. What motivation does she have right now to eat better or exercise? She has a husband who fixates on what she used to weigh over 20 years ago, and labels her as “unrepentant”. I agree with the previous poster, I’d like to know what you mean by “unrepentant”.
Please be kind to her. Help her instead of blaming her. Tell her you love her. Cook healthy meals for her. Tell her you want both of you to grow old together, and that you are worried about her health- not what she weighed 20 years ago. Not that you want to separate until she is “repentant”. You’re married, you’re in this together, for life, in sickness and health. Don’t abandon her because she doesn’t look the way she used to.