You can use AMEX points to redeem on US Airways, by transfering to Aeroplan and then from Aeroplan to US Air through points.com. The rate is something like 1/.8 so it would be about 150k AMEX for a business class ticket to DEL. Of course, US Airways has basically the same availability as UA.
Really quite simple to plan this trip. There should be all kinds of NH, OZ, UA availability TPAC and then connecting to DEL. There are 3 seats open ORD-NRT in business on the 17th. The NRT-DEL NH flight is also wide open, so the connections are simple. Search it segment by segment and you will have success