I brush coppers teeth to keep them clean and I have read that you can add some roughly chopped veggies like carrots to help with glands, I would use a canned or home cooked food with better ingredients before I would worry about glands and teeth which both could be done mannually. I agree that it would be great to have a quality low protein kibble maybe we should make one
I hope that she starts to feel better soon, I understand the feeding frustration, finding that balance is hard.