I am a bad numbers girl, so forgive me. Essentially, you are right. The problem is it becomes a little more complex if you separate. The courts will look at your monthly costs, like your mortgage, bills, food, etc. and they will look at his, rent, bills food, etc. They will then look at your individual incomes and force him to help you to the extent he did in the past and to the extent he can.
This means that if he is smart, he'll go out there and rent a very expensive apartment. The higher his own expenses the less he has to help you. But you have a financial advantage in that he will have to abandon you to do so.
Sorry I cannot be more helpful. I can find the statute citation for you and post it here and you can look at the rules (the NC General Statutes are available online) and do your own math.
