Mona, Trust me, the man has food that he can fix for the children...or better yet, he can take them out for fast food. There are some places that are open on Christmas Day. Trust me, your h won't go hungry.
I'm extremely proud of you...you didn't save him. Don't! He made his bed, now let him lie in it. I think your h was looking for you to say that he didn't have to see the children. He may have wanted to be alone or w/someone else. Gosh, the man used every excuse in the book from, no food, no gifts, to not going to your sister's.
How to deal w/this w/your children. Sit them down and explain to them that dad is living in a small place and is paying rent and doesn't have the funds this year to purchase them gifts. You can state that he loves them very much, but money isn't going very far in paying his expenses this year. It's best to tell them up front so that they aren't asking questions or being disappointed when staying w/their father.
Congratulations on the evaluation!
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.