Those are good signs that he's visibly upset and saying you are a "good mom." Gosh your husband does sound like mine! Keep detaching, but also be friendly, flirty, happy about an exciting future, and always look super HOT (the divorce woman look!) whenever you are around your husband. Seeing this will remind him of what he's missing. Also, make sure you and the kids are doing REALLY fun family things when he's off doing his single guy stuff, take photos of the kids at these events and outings, and give him copies. This will help remind him of the fun family things he's missing by not having an intact family. He'll feel left out.
Now if he happens to bring up any relationship talk, here is what I would do... you might consider trying something similar..... If he brings up the loveless marriage agree with him and say you don't want that either. Even tell him very nicely and generously that he probably didn't love you in the past otherwise there'd be no problem loving you again... and you understand and just want his happiness now... because if you loved someone once you can love them again... your agreement with him, niceness along with a bit of logic thrown in will give him something to think about!
And then say you know eventually when this is all over there will be a great guy out there who is just going to love you and appreciate you more than anything because you are a fabulous woman; beautiful, loyal, smart, have an awesome family, great kids, etc... You are valuable and definitely remind him about that by acting like it and pointing out and all your great qualities... and be very happy about the fact you're going to find that fantastic guy... and assure him that you will find a great step dad for the kids. Someone who is going to love them like crazy and treat them like his own. And then touch his shoulder and thank him for being so wonderful. Always thank him profusely for any little thing he does. Things to help with the kids, etc... (hee hee!!!)
And if he brings up the regret thing agree with that too (agree with every stupid ridiculous thing he says!!!! Even if he's completely wrong!). Then say something like you don't want regrets either and "we're doing the right thing..." then carefully bring up... well we did have some fun times too over these last years. Do you regret it all? Do this very carefully. You don't want him to think you're trying to convince him of anything. But basically what you're pointing out is if he hasn't regretted the past, why would he regret the future? All of this must be done very carefully so it doesn't look like you are tyring to control the situation or convince him of anything. Always let him lead and figure the answer out on his own. All you are trying to do is hint at other angles so he might consider them. Kind of like a socratic method. At the same time bring up special memories every once in awhile, or sayings you had. These will become nostaligic reminders of good things in the marriage.
There is no arriving, ever. It is all a continual becoming.