In the first you are right, but that is a different matter from the Pacific War, as in that War(of the B-P Confederation), many people in Peru helped Chile and fought against Santa Cruz. Argentina pretended to help them too, with not so good results. If we had been successfull, Tarija very likely would be Argentinean today.
And for Chile, they effectively gave up those millions of square miles when they decided to fight Bolivia and Peru for Atacama and not us for Patagonia. Once Argentina controls Neuquen, the best Chile can do is maybe one settlement in the Gallego River, but not further north as we already controlled the Santa Cruz River(Isla Pavon).