I could see anger motivating to keep to the 180 in your particular situation. Afterall, you don't deserve that treatment.
In my case, there has never been arguing, abuse, affairs, addictions. From the outside looking in, we were the ideal marriage. However, we ended up as friends/roommates with children. So, when my wife suggested separation, and I filed for divorce, and then thinking upon it, I realized I have always loved my wife, still do. She stopped sometime ago. She requested to be friends. She loves me but is not in love with me.
I, however, still love her. So now, I have to "unlove" her in a way that allows for friendship, but nothing more.
And considering there is no other man. That she'd rather be by herself than with me (undergoing positive changes) and our children makes it that more difficult.
Jayb, your situation sounds almost identical to mine. I went through an extremely rough couple of months trying to save it...all to no avail. Then one day, I just said "the hell with this" and we got down to planning the seperation. Curiously enough, at that point our relationship seemed to improve...we spent hours and days talking like we have never talked before. Despite that, it was obvious that she was still totally done, although I thought it was a bit ridiculous how we could get on so well like that....I mean, as we were now getting on so well, surely it'd be worth another go? It took me a while to get over that as well.
We put our house on the market and it sold straightaway. I moved into a nice apartment, her into a new house. Totally split everything 50/50, very amicable. Our daughter is adjusting very well and even seems to enjoy having 2 "cool houses and rooms" as she puts it.
Despite some bumps, at no point have I ever done a "hard 180"....personally I think by doing so would only hurt our daughter. I understand that in some splitups that is necessary....but if yours goes as amicable as mine, there's no real need.....IF (and its a big if) you can proceed with falling out of love with your ex while still being friendly with her. I decided that is what I needed to do - get my head to where hers was. After a couple of false starts, I started making real progress with that. I concentrated on my own areas of disappointment with the marriage...all the stuff that id put up with, all the frustrations etc (and would have continued putting up with them....as I believe that's what marriage is all about, compromising) .
After a while, I really started enjoying my own space. I surrounded myself with friends, many of whom had been through the same thing (or much worse) . Even friends far away....talking about it with people who understand really helps so much. As it stands right now, I'm really enjoying my part time single life, part time dad. I'm at the point now where I have really detached any romantic feelings for my stbx (wont work for everybody but having a bit of a fling with someone else really helped me I have to say), and now I feel confident I can maintain a decent enough relationship with the stbx for the sake of our daughter.
If you have got a similar amicable situation....my take on it is that a total hard 180 will do more harm than good. If you can get your probable divorce sorted without lawyers etc you might as well make the best of the friendliness and get everything thrashed out between the two of you over several beers or something. The key though is you need to detach from her romantically. I still do care about my stbx (and her me), but the fact ive been able to put myself in her shoes, so to speak, has been huge.
Like you, I went through a lot of anger about her tearing the family apart....but now to be honest, that's almost become a defence for me - I'm like "she did this " so feel as though I can now do whatever I want. I seem to have gotten here pretty quickly...others take longer (and no doubt I still will have some twinges ahead) but its the only way to go.