Great shooting, and wonderful news about the ketones and eating - wahoo!! That +2 rise is what we generally call a food spike. His numbers should turn around shortly, and hopefully he'll set up a nice, safe surf.
In general, you do want to consistently shoot the same dose morning and night. New folks who don't have a lot of testing data yet usually follow a "no shoot" number in the neighborhood of 150, and that is when you would consider skipping the shot or shooting a reduced dose. Over time, though, as you gather data and see how Toby responds to insulin, you want to start lowering that "no shoot" number, as NOT skipping shots is what gets a kitty closer to regulation and/r possibly even remission.
ECID (every cat is different), though, and there are always several factors to consider on top of the basic concept of a "no shoot" number. In your case, you do want to keep the infection and ketones in mind, as insulin is very important to keeping the ketones in check.
There are others here with a much stronger knowledge in ketones than I have, so I'm sure they will come along throughout the day and give you more in-depth answers.
Also, we do start a new condo (thread) for our kitties each day (but, at the same time, we keep it to one condo per cat per day). When we create our new condo for the day, we include a link to the previous condo, so others can follow that link and catch up on the previous day's activities. So when you have a chance, can you open a new condo for Toby?
Surf that juice, Toby!!