If he's on dry food, even LC dry food, that means following SLGS. Dry food is processed at a different speed in the cat's body. TR is an aggressive protocol with safety mechanisms built into it, one of those being all low carb wet or raw food diet only.
What is your feeding schedule for Buster? Or is he a free grazer? I notice he does some big drops around +3 or +4. Maybe giving him an extra meal a bit before that might slow him down. A flatter cycle means he's less likely to drop into those brief reduction earning greens, and will also help prevent bounces from fast drops.
If you want him to gain weight, look for low carb food that has higher calories, mostly from fat. The three main components of food % wise are protein, fat, carbs. So lower carb, higher fat might be mid or lower range protein. Getting him to spend more time in better BG numbers will also help him gain weight.
Although this post is written for those following TR, there are some helpful hints for people working away from home:
Is Tight Regulation Possible with a Full Time Job? Yes!
When kitties are newly diagnosed with FD, they can often be dehydrated from the drinking/peeing. Dehydration can elevate kidney numbers, so good to get him checked when he's in better numbers.
Another thing that sometimes helps peeing outside of the box is Feliway diffusers.
