oh, kate, Bless your heart. His threats are doing to you what he wants them to do, make you worried over your decision to turn him out. From what I've been made to understand (and the subject has been present in my own life), threats usually come with little intent. It's when someone is suicidal and says nothing that we need to take notice. This, of course, does not hold true for all, but (again as I've been taught) is a general rule.
Do put it in God's capable hands, as celtic said, and we'll pray for your son's protection. (((HUGS)))