There is a HIX in Cuiaba too, costs R$800 during the cup, or 20000 points (which can be bought for $140) and there was availability (not sure if exactly the same day as the games there).
Azul is the third biggest domestic airline, and quite good if you don't fly to or from Rio and Sao Paulo -more direct flights between other cities. Last time I checked, there was a bug in the site and you couldn't buy a ticket with a non-Brazilian card (just Amex worked).