OP I think you've had a massive scare to be honest.
You mention that you didn't support him through cancer treatment for him to kill himself drunk driving, and I'm wondering if that's at the heart of your upset.
You've both been through something out of your control, something many people don't survive, and now you see him wilfully and purposefully drunk driving and risking his own life, other people's lives, and your family security for no good reason.
And he can't seem to grasp why that's a bad thing or why you are upset because nothing actually happened this time.
I think you've had a shock. I don't think putting it on Facebook helped, mainly because if he doesn't get why you are upset, he's not going to care what your Facebook friends think either.
His work friends clearly don't care, and may have done the same thing themselves, so they are going to think badly of you rather than him.
And it might have jeopardised his job, although you say his boss won't care unless he loses his license.
It's not really the best way to deal with a problem in your marriage, making it public to try and shame him.
But I think Facebook and now the looking at flats thing is just your desperation at trying to make a man who doesn't care about what he did listen to you and your feelings on why it was wrong.
I don't know what might help. I grew up with my parents running various pubs, I've seen all sorts of outcomes from drunk driving. The repeat offenders who just won't stop even if they've been caught, the people who park around the corner and think nobody notices they drive after a few pints, the people who have lost their license and in some cases their job, the man who was hit by a drunk driver and left on the road for over an hour before he was found.
Growing up in those pubs is the reason I reason I rarely drink now, and the reason why I am zero tolerance on myself and won't have a drink at all if I need to drive.
Is there anything on-line that you can show him to try and shock him into thinking about this properly? I'm sure I watched a video where people who drink drive were invited to their own 'funerals' and got to watch their friends and family 'grieve' for them and listen to them give eulogies to try and shock them out of their destructive behaviour, if you can find something like that, would that help?
I'd also ask him to consider looking for another job, because if the problems have only arisen since he started working for that company, it sounds like it's not a good place for him to be.