For the chewing problem go to your local pet store and they should have little blocks of wood for them to chew for about $4.99. Anyway you can buy flavoured or non-flavoured but I don't think it really matters. Anyway I have never owned a gerbil but I used to have a hamster and right now I have two rats and they all loved to chew. I would try the wood blocks if I were you.
Good Luck!!!