Can't help with your car-chasing problems. The girls in the local pet shop say that the best way to cure a dog is to put it on a rope attached to the bumper and drive around a field until the dog's exhausted - but it sounds cruel to me, and I wouldn't do it. They claim that the dog will then associate cars with horrible experiences.They said another thing which sounds more sensible - if you're going to live in the country, you should first introduce your dog to a ram - it'll *never* chase sheep if the first one it meets is a ram!
But speaking as someone who hasn't yet succeeded in teaching my dog to walk properly to heel - she insists that she's the leader - I can't give any advice.
Except on one thing. Don't use electric collars. They may cure the dog (or they may not), but they'll make him frightened of things that touch his neck, and they'll bring out a nasty side in yourself.
I'd build a fence. Can't be that dear. And if you have a fence your dog isn't going to be the one blamed when a dog bites a child.