It's very possible he was abused, but people always seem to assume that fearful dogs were abused, when the truth is that most often its a genetic, inherited fearful temperament. If this dog truly was abused and has a stable temperament, he'll come around on his own and fairly quickly. In the meantime, keep your kids away from him - fearful dogs can bite. The best thing you can do for him is socialize him as much as possible - take him as many places as you can. Do some obedience training with him each and every day and you need to find out what his currency is. Does he work for praise, treats, a good session with a tug or ball? Find out, and use lots and lots of positive reinforcement with this dog. Dogs gain confidence from success, so teach him as much as possible and let him succeed. Your husband needs to get involved with his feeding, grooming, walking and training. Don't give the dog the opportunity hide in the bushes or behind your legs. You're not doing him any favors by doing that. A fearful dog isn't in the thinking part of his brain, their in the limbic (hind) brain. They can't learn anything so your husband needs to start slowly to build trust. Lots of small bites of high value treats, combined with a ton of praise, should work. If you need professional help with this dog, please get it. Inexperienced dog owners aren't equipped to help a dog like him without help.