I would say put him in a kennel durring the day, that way he cant get in any truble. The biggest reason he is chewing is because he is a pup, they chew, they have tuns of energy and when no one is around they get board and cause truble. The best thing that I have found is lots of exercise, keep him so tired that he is to week to cause truble,, no just give him enuf exercise and bonding time. The most important thing to do is start training him to listen, sit , come, stay, this will pay big time as he gets older. Also give him aother thing to chew on, what I did with my dog was gave him a rubber ball every time I had to leave him, he loved the ball and would spend hours chewing it. If I forgot to give it to him I was replacing someones shows.

Good luck with him and dont give up,teach him who is boss.