Been there - my husband of 15 years left without warning. My next door neighbor (father of my daughter's best friend) helped with support and food for my kids (I couldn't function for a couple of weeks). Five years later I married the same next door neighbor. We have been married now for 10 years and are happy together.
As for the son, he will learn there are consequences to his actions and will be better for it (I hope). Love him, support him, and you will both get through this, too.
I won't say "Merry" Christmas because your's will be a trial to get through, but there will be better days coming. You are in my thoughts and prayers.
Janice