It sounds like you are feeding the right foods. You want to try to stay under 10% carbs.
Cats don't have a lot of nerve endings in the ears, and if you give him a treat and some lovings every single time you test, whether successful or not, he should learn to associate testing time with good stuff.
We would ask that you test at the very very least before giving insulin at each shot, and if he ever has a number that you are unsure of, then post here and ask questions about whether you should shoot or not, and what dose to give.
To help you with the dosing, we would want to see some mid-cycle tests too, like around +6 (six hours after you gave the shot).
When you have a chance, can you please set up a spreadsheet, if you haven't already done so? That way we can see how your kitty is reacting to the insulin and help you to help your kitty.