I just want to second the advice by wishing4happiness of finding something each day to focus on besides the house. That is the very thing that has been keeping me grounded in a very trying housing situation until we can get into a new place.
The other thing is sometimes we get fixated on the ideal and NEED it to work, but life is all about
learning to be flexible. Hard when you battle worry, but not impossible. It's a work in progress. So instead of imagining the worst, and/or what will happen if things don't all fall into place perfectly, start thinking of your options. You could always rent in the new city until your house sells. It wouldn't be the end of the world and that's often how people handle moves like this.
We have friends who moved across the country for her husband's new job. They were apart for about
nine months until they finally got things set with buying a new house and then she and the kids followed. But they made it through and are settled in now.
I know it sucks, and can't imagine how stressful it must be to have to keep showing the house, especially with 2 little ones. You are doing well just holding up with that alone. Pat yourself on the back. And remember, this is not in your hands. But trust life/God to work things out as they are meant to be. In the end, it will all work out.
And now, make it your goal to create pockets of joy in each day as you wait for your new beginning to fully come into fruition. You can do it.