Wow,
Bob, sorry to hear that.

It sounds like he should be okay, though; my cat was once hit by a car very badly and the Vet was able to save him (although I had to "insist" strongly-- they wanted to just let him die because he was so badly hurt).
Do you have any details on his injuries? Does he have any broken bones? My cat had to have his jaw wired shut for several weeks and could only eat liquid food.
Your story sounds similar to familiar situation that my cat has been putting through. It's my fault that I let my cat going out playing with his new grandfamily, but none of them want to share that bond with him. Then, one day, my cat wander down on the road to find something new to him. That's where I was on the computer watching him to making sure that he wouldn't go that far. It's my responsible to ensure that nothing that will get him killed. Apparently, his curiosity nearly got him killed in two months ago.
I got distracted for a moment and then turned around and finding out that the red car was intentionally swerved to overran my beloved cat. As a result of that event, my cat suffered a serious damage to his mouth and the chin looking really bad. He was so scared. Next morning, I bought his favorite vitamin pills to making its sounds to calling him out, when he did that, he ran right back to jumping into my arms. It pains me to seeing him suffering like this. My grandmother sounds so heartless when it comes to this situation occurs, she told me herself that most cats heals very quickly. She tried her best to convinces me that, as result of that, we got in big fighting about taking him to vet to taking care to ensure that his health is ok.
Glad to report that my cat is doing all right. His mouth is completely healed up nicely. His memories has floored him pretty heavily, it's reminded him of the situation where the red car overran him, every time he heard the sounds of cars coming on around, he ran back to my room, or ran back to hide behind the electric wheelchair on the porch. It upsets him so violently. I'll take the blame for not taking the responsible to making sure that nothing bad happens to him. Moreover, I blame my grandmother for letting him going outside, because he cried too much.
Now it's my job to making sure that he lives longer to past age of 20. What can I do to making sure that his health is not getting any worse than it is already?