It’s not about finding the right food. What you are feeding sounds fine, especially if the lab work came back good. I would cut the amount of kibble you are feeding in half (1/3rd cup twice a day with a topper) if your vet approves.
Maybe try a grain-free kibble such as Nutrisca. In my experience, small breeds don’t do well with raw.
Do you have health insurance for your dog? I ask because I think from the information you have provided that your dog might benefit from aquatic therapy (swimming). If your vet prescribes it for weight loss it may be covered.
One minute of swimming is equal to four minutes of running and it’s easy on the joints, plus he will get the benefits that exercise can provide, such as weight loss, improved mood, etc.
