sunshiney, I have to admit, I cringed a bit at the e-mail you wrote. It's very kind - but it's extremely full-on. I think you were looking for somebody nice and this man ticks the boxes but quite honestly, if you were the one for him, he would be looking at all his options now to take care of his children without 'leaving' you.
He's not doing that. He's moving back to his old home and regardless of where his thoughts are for his ex-wife, they're really not with you to the same degree that yours are for him.
If you want to stick around - and every post you've written says that you do - despite nearly every poster telling you to cut your losses and back away - then you'll be doing that on the 'never, never'.
You said that you'd be happy to bring up his children (which I thought was a bit preposterous only four-months into the relationship) but he's not giving you that option. It's not in his mind for you to do that and respectfully, I think you will need to back away and take your place in the background if you insist on hanging on.
I really wish you well but, I don't think you're acting in your best interests here and you're lining yourself up to get badly hurt. To negate the effects of that, use your extra free time to make a life for yourself so that if (when) the end comes, you won't be completely devastated having put your life on hold for this man.
Do you have friends you could talk this through with? I'm sure they would rally to distract you and keep you from completely obsessing over this relegated relationship. I'm deeply sorry for you.