Gonzo was a very picky eater, he ate less than 1 cup of kibble a day and he was still usually a few lbs overweight. I've definitely noticed that when he gets raw in the morning and kibble at night, he eats the kibble a lot more happily.

Could you feed raw for one meal, or raw every other day, to just Kaige? You could also try adding an egg, chicken broth, pulped veggies, meat, scraps, etc to make his meals more tempting every once in a while. Have you tried soaking it in warm water?