Thanks for the additional information.
Dogs are aggressive toward people for a variety of reasons. It might be that they are fearful of people and thus are aggressive before the person can be. In other cases, a dog is aggressive in order to dominate the people. Other causes could be that the dog feels they are the alpha member of the pack and as the alpha member they must protect the pack (you) from threats (people).
In addition, owners sometimes make the situation even worse by tensing up and worrying about what will happen. The dog senses the owner worry and feels that he is justified in his aggressive stance because you are obviously worried about the people. They don't know you are worried about them being aggressive, they just feel that you are worried and assume it is the people. This is why a lot of dogs are aggressive when on the leash.
For a dog like this, you must be the boss. To accomplish this, you will need to have the dog wear a basket muzzle anytime he is not in your own house or yard. This will not only prevent bites but also allow you to feel more at ease when walking him or having him loose. Also, most states only allow a dog one "free" bite. With a second bite, they usually will euthanize them.
You will need to have him obedience trained. If you can, I would do group classes (with the muzzle) and let the trainer know of the problem your dog has.. Before you can get into classes, the following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
This obedience work establishes you as the boss and as the boss it is your job to protect the dog and not the dogs job to protect you. Now the dog will still protect you if something should happen because you will be protecting yourself and as part of the pack, he will follow your lead and protect as well. But if you are calm around someone, he will see that you are ok and there is no need to help. This is why being the boss works well.
I think you will be pleasantly surprised at how well your dog does with training. Dogs like knowing what is expected of them and they love the little paper thin slices of hotdogs that I use for treats while training. Give this a try and see how it works for you. Also take him around a lot of the neighbors once he is trained. Use the muzzle so they do not feel threatened and ask their help in socializing him. Ask them not to lean over him, but to crouch down if possible. You can have them give him commands like sit and when he does, let them toss him a tasty hot dog sliver as a reward. Instead of being scared of them, or feel they are dominating him, he will see them as friends and givers of hot dog slivers. It will take work but it can be done.
If his barking gets out of hand, you might consider a citronella bark collar. However, once a dog can't bark to "scare" a person away, they only have the bite option thus socializing him and obedience training him ends up working better in the long run.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer.