You want to start on a low dose (.5 to one unit twice daily) You can always increase as you get hometesting numbers and see how the insulin is working. If the vet says his numbers were high, you can assume they will be lower at home once your kitty isn't stressed out. If he wants to start at a higher dose, you can always get home and start lower, and just say you were nervous starting higher.
You will be buying your own non prescription food. (If you want, you can always take a small bag of prescription food and then return it, saying your cat won't eat it. That might save an argument about food. Food manufacturers will always accept returned catfood.) It would be nice if he would let you practice testing in his office (on the ear) but if not, we can help you learn how. I would ask what the fructosamine test showed and get the numbers for that. Ask if there are any other issues like an infection or bad teeth that might be elevating the numbers.
The trick is to agree to work with your vet but remember you are your cat's best advocate and you will be a partner in making decisions about his care. Good luck and let us know how it goes.