Yeah! for Mr. Kitty liking the wet/canned food. That is half the battle sometimes, convincing a cat that wet food is edible.
With not much data yet, and you switching Mr Kitty to low carb canned food, the numbers certainly can drop 100 basis points or more. So it's a good idea to drop the insulin dose as you are doing the food change. Like you did, from 2.5U to 2U of Vetsulin.
You can always increase the dose, but once you have given the insulin, you can't take it back out.
Did you print out the hypo instructions, and make up your hypo toolkit, just in case Mr. Kitty goes low?
They are in the Health Links/FAQ's forum, in the index. Along with a lot of other documents.
Be prepared isn't just the boy scout motto, it's ours too.
Vetsulin (Caninsulin) often doesn't last more than 8-10 hours in a diabetic cat. But hoping that Mr. Kitty is an exception to that normal and he gets longer duration.