I'd be happy with those green BG numbers and an occasional blue BG here and there. In general, I'd say that Tuko is doing better when he is getting the lower carb Fancy Feast foods. At least his BG trends have been a bit lower since you started to add the FF to his diet.
I think this may be remission for Tuko, diet controlled status. So he is always a diabetic, but diet is keeping the BG levels low.
Here are some tips to stay OTJ (off-the-juice, insulin being the juice)
1. Never feed dry - not even treats. (freeze dried is ok, Dr. Elsey's chicken flavor dry is ok for some cats.) If you change wet food types, be 100% sure the new food is also low carb and same low carb % as your current food. Some cats are very carb sensitive and an increase from 3-6% to 8-10% can spike the BG’s. Don’t feed if you aren’t sure!
2. Weigh every 2 weeks to 1 month to watch for weight changes. Too much of a weight gain can cause loss of remission. Too much of a weight loss alerts you to other issues, such as hyperthyroidism.
3. Measure blood once a week, indefinitely if possible. You want to catch a relapse quickly. Some people only do checks every 2 weeks to a month. BG checks can sometimes alert you to other issues.
4. No steroids or oral meds with sugar - remind your vet whenever giving you any medication. Always double check. (Steroids may be needed for other medical issues. But remind your vet your cat is a diabetic, diet controlled.)
5. Monitor food intake, peeing and drinking. If increasing, a sign of losing remission. Or another medical condition like Hyper-T or kidney disease.
6. Regular vet checks for infection such as dental , ear or UTI. And get them treated quickly!
7.Continue to ketone test even if your cat is OTJ. Ketones can develop if the cat’s pancreas is not producing enough insulin, or burning off too much fat if your cat is not eating properly and other reasons.
If your cat does fall out of remission you need to be more aggressive and resolve issues/ back on insulin as soon as possible as the window for a second remission is tight if any. Pancreatitis, hyperthyroid, dental issues are the most common reasons cats fall out of remission.
"Once a diabetic, always a diabetic." They are simply diet controlled.
Congratulations!