Indy is noticeably more muscular and buffer◊ in Indiana Jones and the Temple of Doom than he is in Raiders of the Lost Ark even though it's supposed to be set a year before that movie. The reason behind this is because Indy would be shirtless through a lot of the movie so they had Harrison Ford work out with a personal trainer to build up his body. If you look at the one shirtless scene in Raiders (when he's on the ship with Marion) he looks scrawny in comparison◊. In Indiana Jones and the Kingdom of the Crystal Skull Indy mentions to Mutt that he almost died of typhus looking for the lost city of Akator. Typhus can cause dramatic weight loss. It's possible that between TOD and Raiders is when Indy got typhus and bedridden for a long period of rime and lost a lot of muscle mass and that's why he's skinnier in Raiders.
Also notice that Indy is refering to a novel that was published only in Germany which has him searching for the city, then known as El Dorado.
Indy's Arbitrary Scepticism makes a whole lot more sense after seeing Last Crusade, where we learn that Henry Sr. was a true believer in the power of the Holy Grail. Right through to adulthood, Indy was playing the Agent Scully to his dad's Agent Mulder because, like most kids who don't get along with their parents, he was rejecting Henry Sr.'s beliefs and ideologies.
Although Dovchenko and Spalko are equal in rank, Irina would very likely have been part of some higher-level secret project related to her apparent mental abilities (likely within the newly-formed KGB), and thus would outrank the regular-military Dovchenko due to her affiliation with the more elite organization.
Compare the leitmotifs for the Ark of the Covenant and the Holy Grail:
The Ark theme is dark and threatening, appropriate for an artifact with such destructive power (as Those Wacky Nazis learn the hard way). Also appropriate given its origins—throughout the Old Testament, God had a thing for smiting those who displeased Him (flooding the world, wreaking havoc with Egypt, punishing His own people whenever they lost faith, etc.).
The Grail theme, on the other hand, has more of a majestic serenity, which suits an artifact that saves and prolongs life (though the same can't be said for the false grails). It also suits its user: Jesus, who was all about love and salvation.
Why does Indy, an American from the Western part of the country, carry a British Webley caliber .455 revolver? Through World War 2 the British Empire covered about 1/3 of the globe. For someone who travels the Earth on archeological expeditions, using a British Army standard weapon is the best way to ensure ammunition and parts availability.