Hi Liz,
My first thought was, He is after getting a release from the death.
It is over. The father is dead.
What was his childhood like?
What really went on with this father of his?
Secondly, as childish as it sounds, the trip gave him the freedom to act like everything was normal. Driving around with his wife and kid, away from all the crap.
He probably really, really, really does appreciate you going with him.
There may actually be a change here. You never know what that change can come from, realizing that his own family are more relevant and important than his family of origin.
I will say one thing though, the biggest enabling behaviour I have a problem with is the fact that you were willing to go in the car with him. What insurance etc would cover you if you crashed? You also are responsible for your son. Bad. That is illegal.
Sometimes, a bad decision can have a positive outcome. A true case of "the end justifying the means".
I hope there has been a "lightbulb moment" for your husband. That would be nice.
Continue or start Alanon, regardless.