Humphrey‘s also on a renal diet and we‘re having similar problems, he has raw beef mince with 20+ percent fat, rice and vegetables and a renal supplement (to compensate for the bone and offal which he‘s not allowed). My vet recommended a nutrionist and she gave me food plan and suggested adding additional water to the food to help fill him up and also encourage him to drink more. I add more water to the rice and cook it for about half an hour longer than I would for ouselves, which also bulks it up and makes it easier to digest. He gets raw carrot and vegetables instead of treats. I‘ve also started feeding 3 times a day, he gets his last meal before we go to bed and that does seem to have stopped the early morning licking his lips and signs of acidity.
Humphrey‘s food obsession seems to have got worse as he‘s got older although I‘m not convinced he‘s actually that hungry, I think its habit/boredom/ age/ cocker spaniel!
Hope you can find a solution.
Xx Jayne