Ash, I think, as others have written, that a really good trainer/behavourist could help you a lot to get to grips with Chewys biting problem, that and what you already know and are doing should win out in the end.
As for perfect dogs, lol, my Bob sure is not one! And, unlike Chewy, Malone, Nebo and others, he is no pup/youngster still, he is nearly five years old! Unlike the other dogs I have had he has just proven to be a difficult dog for me to train properly......I won`t go through his faults or I will just depress myself!

Just keep at it Ash (as I know you will.) Love to you and Chewy.

Chris and Bob, and Ebby the cat of course