Question: Does Schofield throw away his canteen after he pours water over his eyes? In any event he has it again to fill with milk at the abandoned farm house.
Answer: He puts his canteen back after he poured water over his eyes. You can tell because after he gets up it's hanging on his side again.
Answer: Good eye! The gunner's seat in the Douglas SBD was on a swivel. The military rating was actually radioman/gunner, and when facing forward, he had access to a suite of radio equipment and a set of basic flight controls! He could actually fly the SBD from the rear seat, although this is never reported to have been necessary in combat.