Just a couple of thoughts...
How are you feeding Dunkin? Does your kitty get meals only at shot time or are you spreading out the food over the time before nadir? Given some of the drops by mid-cycle, you may want to divide up your cat's meals into smaller portions and provide food over the first few hours of the cycle.
Likewise, routinely getting a +2 test may allow you to intervene with food to prop up the numbers. If your +2 is considerably lower than your pre-shot test, it may signal that numbers are dropping and you would want to monitor to see where the numbers are heading. Using food to steer the numbers can help to level out the cycle and, hopefully, prevent some of the bouncing.
With the newly diagnosed CKD, you may want to look for foods that are low in both carbs and phosphorus. Weruva is one of those brands but there are others that are on
Dr. Lisa's food chart.