POOR BABY !! The only thing I want to say is if you think he's in shock - why are you taking him somewhere ? I would think he'd be more comfortable in his own enviornment rather than travelling.
IF my girls were hit by a car I would not leave their side till I knew they were 100% A-OK. Don't mean to be so blunt
but it's something for you to think about.
You seemed more upset with the driver and didn't say what exactly was wrong with him ....so I'll wish him the best and hope he feels better soon -
but the medication questions are something you should go over with your vet -