I want to second what Jill said. IMO you are ready a lot into what seem like subtle cues. He wants you! If he didn't he would be with OW2, but he's not. He took the step to reach out to you. Now that you both have what you want, I think you are both scared. He's keeping you at be because he's threatened by you as the mother of the children (the OW were safe because he could truly feel they were essentially just a babysitter) and he's down on some of your successes and achievements while what does he do that's so great.
I think it's probably natural to have second thoughts. I've never gotten nearly as close as you and I've had them myself. It's fear. Fear of more of the same and being hurt again. Don't let that effect how you read into everything.
Jo, YOU ARE THOSE KIDS MOTHER!! Nothing he can say, do, or think will ever change that fact. Take this excellent opportunity to renew your relationship with them. It's a blessing.
I sympathize Jo. It's got to be really hard. Hope you can find the patience to wait for things to progress at its own rate. You can't just jump right back into "madly in love".
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
