JL. Please don't be so hard on yourself, I think everyone has made mistakes trusting people that bit them in the butt at some point. Example here...
My hubs co-signed for a new truck lease for his nephew against my advice. The truck was completely loaded to the max. Nephew stopped making payments after the first one and hubs had to fly out of state to get the truck and drive it back, he could not find anyone to buy out the lease and had to pay the early penalty fee to the dealer. He lost $10,000 altogether and was devastated. His sister stopped speaking to him because she thought my hubs should have let her darling son keep the truck! (I think this was planned too) Bad situation all the way around. I never said told you so (well at least outloud; ), he was so hard on himself, too hard. It was a mistake, a costly one, but we aren't perfect and errors in judgment occur to EVERYONE.
Smart move to cancel insurance! I'm wondering though if you loaned him the truck, and then he refuses to return it, wouldn't that be a stolen vehicle? You didn't sign over to him, loan means returning at some point, didn't happen so stolen. I know laws vary state by state but someone else I know did same thing loaning a car to a friend and reported it stolen, and got the car back.
I think we all notice in your post your disappointment that this guy is a deadbeat Dad, the opposite of you. Please be proud of being a good parent. As Dee said, please do not drink over this, it will only make you feel worse.
We are all pulling for you JL!