Please make sure you're home testing before changing the diet! Removing dry food from a diabetic cat's diet can cause dramatic drops in blood sugar levels, and 4u is a pretty high dose. You may find once you start home testing that it is already too much insulin. Blood glucose values obtained at the vet's office are generally inaccurate--stress can artificially raise a cat's BG several hundred points so they are not a good way to determine if a dose is working. Unless you're testing several times a day it's impossible to know if the blood sugar is generally high because you're giving too little insulin, or too much insulin. Overdosing can also cause high numbers because when a cat's BG drops too low, the liver will dump glucose into the bloodstream to counteract the low blood sugar.
There's nothing wrong with the AlphaTrak meter, but the strips are expensive. You don't have to use a pet meter--human meters work just fine and the strips are much less expensive. You want to make sure that you have enough strips to test several times a day, so if the cost of AlphaTrak strips will limit your testing, I would return it and go with a cheaper option instead, like Walmart's Relion meters.