Only 1 open jaw allowed, so add ORD-MIA to the end of the flight. The OW130C award allows 14-20,000 flight miles and your itinerary is about 14,500 miles, so you have lots of mileage to use. Unless, your MIA-LAX-BNE is only a transit, in which case the mileage drops to just under 14,000 miles and a cheaper award.

You must still fly 2 non-AA Oneworld carriers. No way around that requirement. Perhaps a MIA-SCL-AKL-BNE on AA/LA/QF, then you could then fly FCO-ORD nonstop on AA.