Rescued dog very fearful

Question
18 months ago I rescued a chow mix who is about 5 now.  He had come from a situation of being locked in a trailer home with 18 other chow mixes and left to die. All but 4 of the dogs were dead by the time rescue workers got in to help.  He is very, very fearful.  Over the last 18 months we have worked on getting him more comfortable around other people and dogs but he is exhibiting a couple of traits I am concerned about:  he barks incessantly at every little noise he hears (we live in an apartment), and he acts as if he is herding my parents when they get up to leave the group and go a few feet away.  He pounces at them, barking, and recently nipped my mom lightly.  Is this fear aggression?  What should I do? He DOES get plenty of exercise, over an hour a day, he lives in a quiet environment with just me, his owner (female, 43 years old), he has learned to be affectionate with me, does not soil in the house, walks on the Gentle Leader well but pulls terribly when on a regular leash of any kind. We have not done obediance classes or dog parks because my first attempts were met with him shaking uncontrollably, ears flat, peeing on the spot, hiding, etc.

Answer
It sounds as if he might have border Collie in him,as those are traits of Border Collie type dogs

You can try training again,as I have worked with abused dogs in my training classes-and some trainers will only work with you and no one else and in some cases may come right to your house,so call around and explain the situation of the dog

But you can also train the dog to come to you on your own-when he tries to 'herd' people use a treat and call his name and say 'come' and some people have luck with something called a 'clicker' you click that and call his name and give him a treat and you can use it for a number of commands

As for walking you might need to use something that's called a 'prong' collar,it looks scary but it doesn't hurt the dog-in fact it is less dangerous then a choke chain,and when the dog pulls and it 'pinches' the dog it reminds the dog of being scruffed by it's mother as a puppy