Hi
I have only ever been a lurker but I wanted to come out of the shadows to offer you support as I have been exactly where you are now (except without children, so not as bad)
My husband left in the same circumstances and then came back to 'try again' but actually did no trying. That period was the worst because I was so desperate for him to stay that I was walking on egg shells and compromising the entire time. Believe me, sometimes having them back, although you think you want it, is never going to be a happily ever after option.
Anyway, after a month or so he decided he never did love me after all and left again. I remember the turmoil well. I remember thinking that crying just didn't cut the pain and I remember the no sleep/no eat/barely functioning days.
I just wanted to pass on some warnings, although I never thought him capable, (he might not love me, but he isn't a bad person etc etc etc) he cleared our joint account of around £2k and left me in debt. So please safeguard any finances you might have. You really don't know what he is capable of any more.
Also I want to reiterate the getting a solicitor on to it. My exh did as someone up there ^ predicted and said the whole we don't need a solicitor, we can sort it through the courts etc. No! Get yourself a solicitor, you don't owe him anything at all. And a solicitor will get you what you deserve.
Just to finish the story and to answer your 'how might it work out for him?' question. It turns out that my exh also had traded me in for a younger model who had turned his eye. Unfortunately for him she was a bit of a bunny boiler and within a month or so she was pregnant. They certainly didn't live happily ever after. From what I've heard they had a short disastrous relationship and he ended up bitter and single. He actually phoned me a few months down the line apologising and he sounded really sad. Fortunately by this point, difficult as it was I had taken the Silenceinthelibrary approach and was the happiest I'd been in years.
6 months later although I'd vowed never to fall in love again I met my now dh and we got married 2 years later. I am living that 'happily ever after' and that event which at the time floored me and thought was my darkest hour has turned out to be the best thing that has ever happened to me.
Time is a healer as the saying goes. And it is a saying for a reason, it's actually true. For me those dark days when I could throw up from crying and could barely function lasted about a month. Then the determination set in and life turned around. It does get easier.
You're doing fab so far, far better than I did in the early days. Keep on keeping on x