You must still be somewhat shell shocked over such a quick bomb to divorce time.
I too have 50/50 custody and the parenting plan requires each to give 60 days notice if moving more the 15 miles away. I think it would take some serious circumstances for your X to be able to change the custody agreement.
F_KITTY makes a great point about the burdeon of fulltime single parenting. In your situation, with 3 young children, it would be difficult to juggle house keeping, employment and taking care of the childrens needs.
I cant help but feel a little schdenfreude about your X finding that the grass is not necessarily greener outside the marriage.
