40 is normal for a non-diabetic cat. Probably that's what Rooh was before he was diagnosed, and if you tested your civvies (the piglets, LOL) they likely are in that range. We use the 40's as a take-action zone to prevent them from going lower, but we have had cats on OTJ trials that were in the 30's. If a cat's not on insulin, that's fine, but for our kitties on insulin you want to pull them up at that point. I caught punkin at 32 once and nearly had a heart attack - but he was fine and had no symptoms.
You don't need to give carbs for anything over 50. Sometimes giving a couple of teaspoons of low carb can help a kitty surf along in the green numbers.
What you're looking for is how low the dose takes Rooh between the bounces. The idea with reducing the dose is that hopefully, you'll continue seeing green nadirs in the subsequent cycles. If you see nadirs that are higher, then you want to go back up in dose right away. That can be tricky to discern, so just ask for help looking at it.