Hmmmm. Puzzling to me. That's a pretty hefty dose to be giving you this sort of pattern.
I apologize for not knowing Bubba's history in detail, so bear with me. He just had surgery to remove an eye, is that right? Is he on any meds right now? When was the last time he saw the vet? Have you shared his recent numbers with the vet?
I'm not surprised to see an increase after eating. Even if a cat eats zero carbs, the food will still cause an increase because they convert fat and protein to glucose. But once the insulin onsets, the numbers should start to go down. In general, his pattern is pretty flat since his surgery, even though you have been increasing. I'm wondering if there is an unseen infection or something going on, or "post-op pain". Cats are pretty good at masking pain.
Grasping straws maybe but I'm scratching my head here.