Feeding and Dosage question

I posted this on the ProZinc board, but also wanted more feedback if possible.

Oliver has been on ProZinc for a week now and I haven't seen much improvement. On Wednesday we started trying to switch him from Dry to Wet and it has been somewhat successful. He is 17 lbs and the vet said we need to get him to around 14lbs so we have been trying to feed him on a 400 cal diet to help with that. My biggest questions is how much is considered a meal to be able to give the insulin? We were doing a half a can of wet in the morning and for the most part he did well eating almost all of it and once it was gone I would give him the insulin. If he didn't eat all of it we would get him to eat some dry to make sure he had enough in his system. We also have been leaving out small amounts of dry food for him to graze on during the day and overnight to make sure he is getting his full calorie intake and because he would just sit and meow at us if we didn't. We tried doing a whole can of food, but he just wouldn't eat it all and it was then hard to tell how many calories he has eaten. Any feedback would be appreciated.

We are starting to home test, but haven't made it habit everyday yet.
8/11- PM 307 (lowest reading yet)
8/13- PM 340 ( highest since DX, but was a little later than normal)