Hi Tals! Glad you made it over here!
I think since you've gone to 4.0 tonight, I'd stay there and try to get more tests in so you can have some confidence in what this dose can do. When you see green numbers again, think of it as "YIPPEE HE'S MAKING PROGRESS!" Those green numbers are normal for a non-diabetic cat, and to protect their body the sooner a diabetic cat gets back into normal numbers, the better. High blood sugar is damaging to a cat's body.
What Sienne is saying is that there isn't anything to say this dose is too high for Shimi, although with the Start Low Go Slow method, you would reduce when he goes under 90. The thing is, I'm not sure you can jump in at 5u or so and then decide to follow SLGS. I would second her suggestions to please test twice a day or so for ketones and get at least one before-bed test in. Those are really important.
It's a confusing situation, but we can help you work through it. A little more info (ie, tests) will help us help you figure out how to move ahead.
You may need to go back up in dose, but if you're wanting to have it be a little lower so you're less nervous, that's ok for the moment. And as you saw today, a little sugar water made you able to steer his blood sugar. It rose up very nicely. You will be able to steer his blood sugar like that again and he will respond to the carbs you give him. Next time it might be easier to use a couple of drops of honey, karo syrup, maple syrup, or if you have some gravy cat food, you can squeeze the gravy out and give a teaspoon or so if it. Any of those options are probably easier than trying to make a sugar water solution.
Cats develop more capillaries as their ears are poked. It seems to take about 2 weeks, and then you should get blood every time you poke. In the meantime, the poking is stimulating the capillaries to grow, so it's still doing something. Are you putting Neosporin with Pain Relief Ointment on his ears? I slathered quite a bit on punkin's ear at night and it was healed by morning. Wiped it off before the first morning test and he was good to go for the day. If you don't have that where you are, look for a Polysporin with pain relief or something similar. It's the pain relief that's the important part, although you can't use teething pain relievers on cats. A treat after poking will soothe his dignity and make the whole thing easier.
Great job handling things today! It will get easier and less nerve-wracking.