You've been doing great -- and so has Idjit!
A couple of thoughts to add to Sandy's and Stacy's comments.
Your vet was suggesting to test at around +6 probably because the assumption was that this would be the lowest point in the cycle. Unfortunately, there's no guarantee that the lowest point in the cycle (nadir) is reliably at mid-cycle. Nadir can and does move around and some cats have their nadir either early or late. For example, my kitty's nadir was usually at around +3, except when it wasn't. Getting tests at various points will help you to get a better feel for when insulin onset and nadir occur.
It is very important to get some tests during the PM cycle. Many cats' numbers drop in the evening. Without PM tests, you don't know if Idjit has earned a dose reduction and you don't know if his numbers are dropping to a point where you need to intervene. It helps to remember that testing is your most valuable tool when it comes to keeping your kitty safe.
As for the Hill's dry diabetic food, it is crazy high in carbs. It is truly not a "diabetic" food. Also, look at the ingredients: Chicken By-Product Meal, Corn Gluten Meal, Pork Fat, Brewers Rice, Wheat Gluten, Powdered Cellulose, Pork Protein Isolate, Chicken Liver Flavor, L-Lysine, Whole Grain Corn, Lactic Acid, Potassium Chloride. By-products are not muscle meat, which is what cat's need. Corn and wheat gluten are "alternative" protein sources that cat's can't digest and are often sources for allergy. Cat's can't digest rice, either. Cellulose is wood/plant fiber. Cat's are obligate carnivores. Their system is designed to digest protein that comes from animals, not plants. They also need moisture in their food since they have a very limited thirst drive. Dry food contains no moisture, making it hard on the kidneys. This is my long winded way of suggesting you ditch the dry food. If you're looking for a treat or a topper for Idjit's food, many of the cats here are big fans of freeze dried chicken.