From here on out if any of your thoughts revolve around thoughts of what he would think / do / feel. DROP the thought. If you want to do something... GO DO IT!!
Your thoughts and actions going forward are strictly about you and the kids, in that order.
It is time for you to distance yourself from the drama and the best way to do that is to limit contact. Only text your H about the kids or schedules. STOP reaching out to him, STOP trying to get answers to questions, just live life Sandy's way. If you must, role play him being away on business and you being home with the kids. Do all of those things you would on any typical day. Let the wonder, the uncertainty, the fear, go.
It is trying at first, but with just a little determination, you will amaze yourself at how well you can cope and actually move to thriving. It works, been there, as have many others. The key is get started.
Set some simple goals and set your sights at achieveing them!
Give a list of 2 goals you want to accomplish just for yourself by the end of the week. post them here and we will give input if needed. I think you will be amazed with the results.