I can totally relate to all this. My Yorkie is 8 mos. old and is still chewing EVERYTHING. He has even chewed the trim around my front door and base molding from the wall. He's like a little goat. I don't know when it should all end, but we've bought every stinkin' chew toy imaginable in lots of different textures and none of it has helped. Sprays haven't helped either.
I'll keep my fingers crossed for you as I am in the same boat and can't see an end in sight.