Its a self defense mechanism, and perfect normal. You do it so she cant say anything to hurt you further. The reason your hurt is cause you never really had a say in the demise/reconciliation of the marriage, you put in an effort and you don't think she did.
What you have to understand is, it was months or maybe even years she battled with the decision, you just missed the signs, and granted she never really told you, but you probably suspect something wasn't right.
Being cold right now, makes it your turn to move on in your own way. That's what she did to move on. For you it was a short cycle, for her it was an eternity. Maybe, just maybe, she'll remember the good times, but not anytime soon.
Theres no time frame on when the hurt will start to disappear. Your at a stage that you need to just grieve the loss of your marriage, only you will decide how long that will be. Don't be in a hurry to speed thru the process thou, those are your feelings and you need the closure to move on. Dating is a way to try to speed thru the process, when your done, you wont even question if its the right time or not, it will just happen.
In regards to your kids being left alone, that is scary actually. That is WAY to young to be left alone. How can you do it without coming off as vindictive? That's the million dollar question, you've raised your concerns, she's not listening. Let me ask you this, what if you were to find out one of your children got seriously hurt during one of these periods, how do you think you'd react? Angry im sure. I'd probably teach my kids how to use 911 first. Make sure they have a plan IF something did happen. Are any of your former neighbors friends with you? know whats happened? willing to keep an eye out for the sake of the kids? Without going behind your back to your wife and making a bad situation worse? Its a very fine line for sure, maybe just call the police desk, without details, and ask for some advice?