I'm so sorry this has happened. I don't know if he was drinking or not. The way he was acting could be from concussion, but it's obvious he is trying to manipulate you with all the texting. Whether he has all those injuries or not, he'll be okay. He's in a hospital, so that's the best place for him. As you said, you can't fix him, so worrying about it won't help. If he gets a DWI, that will be his problem, not yours.
Now, the car. Do you have rental reimbursement on your insurance policy? If you do, you can rent a car for the next week or so. If not, you'll have to find another way to get around. Does anyone have an extra car you could borrow for a while, until the insurance company pays out?