I would make you several recommendation
s.
1) If he were my dog, or coming to me for training, this dog would learn very fast how to be a dog again, and who was in charge of his life. Dogs do not understand any living arrangement except a hierarchy. If YOU are not in charge, the dog will feel he must take charge. See here for how to unravel that without having to get physical with your dog:
http://www.chowwelfare.com/cciw/alpha.htm2) He needs a training class. ASAP. If he is not neutered I would be having that done TODAY.
3) sometimes undesireable behaviors like barking can be managed by being put on what is called "stimulus control". You teach the dog to bark on command. You then reward him for barking when you ask. At the same time you reward the dog also for being QUIET when you ask. You don't ask for the bark behavior if you dont' want it, and if it comes up unwanted, you then have a quiet command to use. Here is how it works.
Each time the dog is vocalizing, give this behavior a name. Say "GOOOD, "say woof". (this is my speak command, just because I think it's cute, but you can use "speak", "bark", "say it", whatever. Say the name you want the behavior to have, and food reward the dog. He will quickly learn to vocalize for the treat. Then you can hold the treat, and when he vocalized, say AH AH, quiet. When he's quiet, say GOOD quiet, and give the treat. He will quickly learn the difference. Now you have a 1ay to quiet him. Sometimes a hand around the muzzle can help with a moment of quiet for you to reward.
I felt before that the barking of this dog in so many different circumstances was the beginning of an issue, but did not want to step in because you indicated it was not really a problem.
These behaviors have a way of escalating if they are not addressed, and it appears that he has (in his mind) been so successful with his barking behavior that he now feels it is ok to disclipline people by using his teeth.
Here is some information on how to teach BITE INHIBITION in dogs. It works for any dog, and is an especially good exercise for puppies.
There are several good articles here, and this is a good site for a lot of training info:
http://www.doglogic.com/apdtfaqs2.htm#bitelynI would also work with this dog consistently on body handling, which is pleasant for the dog, but definitely puts YOU in the leader position.
Have the dog lie on his side with his back to you while you give body massage. All over the body. Handle the head, hold the muzzle while you inspect the ears and massage them. Lift lips and look at all teeth, and open the mouth. Work backwards down the neck all the way to the rear. Make sure to carefully handle each foot, and inspect armpits and genital areas. It's a good idea for all dog owners to do this once per week. You can head off many medical issues in their early stages by being familiar with your dog's body. Puppies trained for body handling like this have no issues at the groomer or the vets, and are easy for YOU to medicate or inspect at home as well. Some dogs will need to be held down for the first few sessions. Balance the body handling (which many dogs find not very pleasant in the beginning) with very pleasant massage, brushing, rubbing, etc, so that you have very little struggle in the beginning. Work up to the point that you can hold your dog's muzzle without any struggle (this is one of the most important parts of leadership body handling....yo
u control the muzzle, you control the dog....a main reason why many dogs resist this form of restraint. It's important for a dog to learn that you can and will control his head. Dogs can learn this with almost no struggle if you start with very short periods of control and work up gradually combining it with the pleasant body handling.
If you will work on these things, and consult a trainer in your area, your barking/nipping issues will resolve themselves, I do believe.
In the meantime, and really, this is ALWAYS important, CONTROL the interactions that your dog has with the public. Control the dog, control the people. If you don't want people petting him for a while, when you take him out, tell people "sorry, he's in training, maybe next time." When they ask to pet him. As mentioned earlier, many dogs do not like to be touched on the top of the head or body. This is a dominant gesture, and dogs may feel it is RUDE and AN INVASION OF THEIR BODY SPACE when someone who is not a pack/family member touches them in this manner.
Encourage people to touch the dog on the chest, or under the chin.
I really get the impression that your pup is just a little too big for his britches. If you take the right course, he should learn quickly that he is not the head of the class, YOU are.