The only way to stop a fearful dog from barking is by slowly desensitizing him to his fears. Socailize him as much as possible, and work him with things he knows, like sertain tricks. When he does something good, praise him lavishly for it. This will help to build up his self confidence.
Begging
Several factors could be causing your dog to beg incessantly. First, you could be under feeding him. An underfed dog will out of neccesity try to find more to eat.
If your dog was once a stray or shelter animal, at one time he may have had to struggle to get food. If this is so, he might retain a very high food drive for much of his life, which could precipitate the begging behavior.
The most common cause of begging in a dog, comes from the actions of the owner, who may have gotten into the habit of giving his or her dog too many leftovers or treats throughout the day. The dog then gains control over the owner, and the owner unknowingly loses more and more pack status until he or she is plainly viewed as a subordinate.
The solution:
Make sure your dog is at his proper weight, to ensure he is getting enough food
Feed him on a regulay schedule instead of free feeding all day. By doing so you will be able to teach your dog that he gets to eat at a prescribed time, instead of throughout the day.
Give him treats only when you are trying to encourage a particular behavior. If you feed him random treats throughout the day, you will condition him to beg more.
Never feed your dog from your dinner plate. Also, do not feed him food made for human consumption, as this tends to teach him that he has equal status with you. Everything you do with your dog should teach him that, thought loved, he is below you in the pecking order.
Never give your dog food while you are preparing a meal at the kitchen counter. If you choose to give him something, put it in his dish instead, at his prescribed dinner time.