Hi,
Please don't use a muzzle to stop barking!
Dogs that have been "trained" in this way are showing avoidance to the muzzle, not a desire to stop their barking! You are gaining nothing, treating the symptom but not the disease!
Your puppy is bored!
He has established a pattern that is unnatural and must be broken. Your puppy needs stimulation, training and excersise to the point of exhaustion on a daily basis. Put him to bed at night a happy, tired and well fed pup and your problems will disappear.
Even if you can't be with him until after work free running then some training work and then a game of fetch and some more free running is all that is needed. Your puppy will be mentally and physically tired and will have had the attention it is craving. It will be able to sleep and any calls for attention during the night should then be dealt with in a no nonsense manner. It is not allowed, end of discussion!