Our GSD runs through our Invisible Fence and attacks other dogs. We try to correct him both verbally and physically but it doesn't work. What can we do?

As I read your Q&A's I see that I am not the only person out here with a problem dog. But I just may be the only one here without a clue as to what to do.

We have 3 dogs and a cat at our house. The first was the cat. Then I moved in with a Shi-tzu(8-9 years old) with a bad attitude. Yes she came from the pound and I make the excuse that she must have been mistreated before I got her. She will bite me at any given time! The only reason I took her in the first place was because this dog picked me out! Never before have I seen a dog as determined to be "owned" by someone as she was. Thus, she is mine. 2 Years ago we got 2 pups from a pet store.

A Chow female and Shepherd male. Both were within a month of being the same age. Things started out bad for the Shepherd and he almost died from a worm medicine overdose given at the pet shop the night we brought the pup's home. He spent most of his first month with us either in the vets or staying at the vets. I guess like one would do with a sick child, we spoiled him rotten once we had him back home and he was gaining back strength. The chow was always sweet natured. Something I found hard to believe from a chow since I had raised them for years and found them to be stubborn, and rather unfriendly to strangers. This one is the one in a million for disposition.

We started having problems when the Shepherd started to try and control the chow. She would take it for so long and then all hell would break loose. As puppies, we could separate them with no problem. Then as they got older, it required more then just picking them up. We built separate pens for them and that sort of settled the problem. Now we invested in the invisible fencing. The chow took to it with a minimal of problems. But the shepherd now 2 1/2 years old is our problem. He doesn't seem to feel pain. With the fence and his collar turned up to full capacity, he still runs through it and will attack any animal outside his boundary. The neighbor has a yellow lab about 1 1/2 years old and he has attacked her several times. Each time outside his boundary. Once in her own yard! An attorney that lives down the road from us was jogging with his dog, which was on a leash, and the shepherd ran through the fencing and attacked his dog! Nothing we do works. We put him in the pen for punishment but he still doesn't get it. When he attacked the lab the last time, my husband put him on his leash and was taking him to the pen all the while letting him have it verbally about how bad he was when he suddenly jumped up on him as if to bite him. My husband tightened his hold on the leash and shortened the length until he got the dog to the pen and got him in. This told me that our shepherd could and would very easily bite us. And as I am sure you have figured out by now, he has been trying to be the dominant one here for a long time now. A wire-handled fly swatter is the only thing he fears. Pick it up and he hits the ground. But that works in the house. With 3 dogs in our family we are at our wits end as to what to do. The Shitzu is now around 13 and won't be here much longer. She will live out her last days here no matter what. The chow is no problem at all. But we need some major help with the shepherd. Is there hope for him or is he so far gone that we should put him down. I know that if he will attempt to bite us, he will definitely bite someone else. We love this dog and will try anything to try and correct the problems if we can. But if the problem lies within his breeding, which we know very little about, we understand that putting him down may be the only choice. What do think of us having a canine officer take him out for a few hours and trying to work with him? Do you think a canine officer could tell if he was worth saving or needs to be put down? Any help here would be greatly appreciated before someone or something gets hurt really badly.