I have done this. I bought separate ticket from NC to JFK and JFK to Delhi. I will never recommend anybody to do this. I also got $300 cheaper but ended up paying more. In my case my flight from NC to JFK was delayed. Because of this, i missed my international fight from JFK to Delhi. Since it was not in one package, i had to pay $500 more for next day flight from JFK to Delhi. Also i always had to worry about luggage. They have different weight criteria on domestic and international flights. On returning back, i had to hurry up so that i do not miss the flight again. Based on my experience, the hassles you will get is not worth it.