Rescue Dog with Dog Aggression-help

[mriver]

We've had our Golden Retriever rescue for over a year. He will be 4 years old soon. He was rescued by a GR rescue group from an owner that kept him chained to a tree at a motel with no protection and only a picnic table for a bed. We know he was abused by some teenagers quite a bit and he also had to deal with Coyotes and other wild animals. Since he was 2 1/2 yrs old when we got him, we know he had little or no socialization. He came to us with a lot of issues including separation anxiety, dog aggression, little or no training, underweight and with a horrible ear infection. We have come a long way with him. He is now neutered, but was not until he was rescued. We have helped him through a lot of his separation anxiety issues, but the somewhat normal behavior is mainly when we keep things in a smooth, repetitive order. He doesn't get frightened now when he's left inside our home, but if we lock him outside with his doggie door closed, he will tear it apart to get inside. Being near us or in his own environment has helped him be pretty content. He also travels with us in our RV and has gotten used to the RV as his second home and is pretty good with us leaving him in the RV while we go out somewhere. Since he was used to sitting on top of a picnic table his whole life, he does sit on the table in the RV to look out the window for our return, but he doesn't try to get out or bark or whine. He feels pretty comfortable there. We have worked with him on obedience and he is well trained in most circumstances. He knows the boundaries of our property and will stay out front with us without leaving our property line. He waits at the door for the invitation to go outside with us and has a doggie door in the back that allows him to come and go as he pleases from the back yard. He has NEVER had one accident in the house. He is very smart and very loving. He sleeps in his crate, but the door is left open. He seems to be terrified of being confined to a small space, but since he doesn't leave the crate at night with the door open, it works for us here and on our trips. This is a long post, but I thought some background and info on his current status. Our biggest problem is his aggression towards other dogs. We have worked really hard on that problem, including hiring a trainer who worked with us and wanted to use a shock collar on him when she finally brought him to social times with other dogs. We used it once or twice, and it did get his attention, but it did not change his attitude towards another dog. So I've been working really hard on distractions. I make him sit and look at me and give him treats. We stay at a lot of RV parks and he takes a lot of walks with us and we always have to be very careful and aware of other dogs. I'd say we are probably able to get him to ignore the other dog about 50% of the time now, but he can also lurch and try to bite at another dog at the drop of a pin, especially if the other dog barks at him, makes any eye contact or lurches towards him. We are doing quite well with him as far as keeping him away from other dogs, but he is such a loving and playful boy and he doesn't have any idea how much fun he is missing by not playing with other dogs. I also worry about the chance of us not seeing another dog soon enough to distract him. Sometimes he will just ignore them on his own. For example, we have two dogs next door now that bark at him EVERY time he goes in our backyard. At first he would hit the fence and act like he was going to attack the other dogs, but we now have him walking past them and ignoring their barks. I always tell him what a good boy he is everytime he ignores them and just lays down on the cement on our side and pretends they aren't there. He knows we will not accept him going after them, so he has learned to obey our wishes, but having a fence between makes it much easier than when it's just a leash. I was hoping to hear from others that have had some successes on desensitizing their dogs to other dogs. Of course, it would be ideal if he'd actually like other dogs, but at this point, we'd be happy if we could see him ignore the other dogs all the time. Are we asking too much? We will love him and give him a wonderful home whether he learns to accept dogs or not. By the way, he seems to love all people. He's great with our young grandchildren and our friends, etc. He will meet new people in the RV parks and loves them to greet him and pet him. He does occassionally bark at someone out front of our house or a skateboarder going by, but hasn't shown any aggression towards humans. Thanks for any help.