They used to think that eating dry kibble helped keep the teeth clean, but in actuality it does little to nothing because the kibble basically explodes when the dog bites down on it, if the dog chews its food at all, so it does not scrape along the surface of the tooth and does nothing for the gumline where most problems develop. So go ahead and add the canned to the kibble and you can even add a little more water to it. The stomach handles wet foods easier anyways.
Protein level should not be a problem. You could try changing foods and see if it helps the one with tearing issues. Feeding variety is as healthy for dogs as it is for us.
