we took our 3 year old Lexi to a new vet and when he saw her teeth asked us if she is a chewer. and if so he was curious how her k9s were so worn down at 3 simply from chewing on rawhide. we realized her favorite ball outside was made of extremely hard plastic and she carried it everywhere. the ball had worn down her teeth so much we were forced to ditched it. We also fostered a dog that was confined to a cage 24/7 w/ his previous owners and we noticed his teeth (all the front and the k9s) were worn to a nub from chewing at the cage.
so there are many good and no so good reasons the k9s could be worn down. as long as he is good with you and your family i wouldnt worry like pp said just be patient and consistent.
regarding the fast eating. our boy pepsi when we got him he gobbled his food so we looked into a bowl to help. below is a link to a similar bowl we found at petsmart. but when you go to petsmart online you cant find the bowl.... it seems to have helped pepsi you might want to give it a try.
http://www.shopping.com/xPO-Brake-Fast-Dog-Food-Bowl
good luck and welcome!