He's loaded and driving a weapon made out of tons of steel. And you are in the passenger seat, risking your life, with full knowledge of his condition.
In hindsight, it might have been a public service to refuse the ride and instead, called the Police.
There is nothing you can do to make this relationship work. You are not that powerful. None of us are.
Let's start to apply some logic here. His addiction is not personal. He's not using at you. His brain has been rewired to protect and sustain his addiction. The only person who can get and keep him sober is him. And right now, there is nothing to suggest he has any intention of doing so. That's alright. It is his life to live as he sees fit to do. Only you can decide when you want to stop living this way.