Storm Rider, I am so sorry to read that he's on the train bound for no where at this time. From all that you have posted, your h could very well be in MLC and is still in replay. Wanting a sepation/divorce is par for course for most of them. It's the only way that they can see themselves moving ahead and not having the full responsibility of being a spouse and a parent. It's their way of telling us it is over and that we need to move on as well. I don't see him moving further along until the "separation and/or divorce" are final. He's in a holding pattern right now. Once the papers are signed, he most likely will begin to act like a bird who has been released, i.e., the euphoria will be an extreme high for him. However, that will only last for a period of about 6 months.
Review your documents well...ensure that you and your toddlers are well taken care of in the style in which you have been living w/your h around. This is your opportunity to be specific as to what you and your toddlers require in life. You will also need to set some boundaries once all of this has been taken care of.
I realize that you would rather have him home w/you and your family, but he's not the man you knew and it would be entirely too stressful on you and your children to have him there w/you while he's searching for himself. Live your life to the fullest, but you can leave the door ajar in case he wakes up and wants to reconcile w/you. Ultimately, it will be your decision as to whether you want him back if and when he comes knocking on your door.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.