I agree with Zero on all his comments except on the above regarding battleships.
Battleships are allowed their special one shot only if they were not involved in a naval battle. If the battleship is present in the same SZ as a naval battle, it has to participate (just like any attacking transports present). After the naval battle, the battleship’s turn is done and it cannot fire its special one shot onto the land battle.
Wild2000 is right. Silly me. That’s a house rule we have that Battleships can participate in both battles. Silly me.