Anabus,
You are right to feel sorry for him, he is sick, he is an alcoholic. You are the ENABLER of this alcoholic. This means YOU ARE MAKING IT WORSE!
If you really love him, turn him in. It will better for the people he might hurt the next time you let him drive your car (which as Starflier said you are already planning to do), it will be better for you because you'll know he will be able to deal with his legal and health issues, and most of all it'll be better for him.
He doesn't have to know its you turning him in. This can be done confidentially. Please consider this.
At the very least do not let him drive your car again. For crying out loud you are breaking the law at that point!