How much does 1 unit of novorapid (insulin aspart) make blood sugar go down?

Individualized. The answer depends on the severity of your disease and degree of Insulin resistance. It's different for different people. For some, 1 u can lower bs by 80 points, whereas others, it will lower it by 3 points. The only way to know is to observe what it's doing on you.
It depends. We will often refer to an Insulin sensitivity factor/correction factor to help make this determination for each individual. Far from perfect, we use a calculation based on estimates of Insulin sensitivity to figure out about how many mg/dl blood sugar will drop per unit of short acting insulin.