Until you manage to stop the chewing, see if you can find Lupine harnesses/leashes anywhere near you.
My mom uses these, and they are guarenteed for life - no matter how it broke! She bought 2, and every time one get chewed up (or run over by the lawnmower
) she just brings it back to the store and brings home a new one! So handy, and 2 will last you for life! (Plus if your furbaby outgrows one, just make it break and replace it with a bigger one!)