1. 500$ is the average price.
2.
Copa (CM) offers 2 daily flights from Panamá (PTY), maybe you can connect on Houston (IAH) or Miami (MIA).
Air Canada is a good option via Lima (LIM), it's possible to flight the last leg on LATAM or Avianca (AV), another option is via Sao Paulo (GRU) and the last leg on Gol (G3).
3.
Avoid BOA (OB) at all costs.