Re: TRS
<Star City exists, but indeed not in Kazakhstan, but near Moscow.
In the movie, the Russian secret engineer is shown as a bald , sinister guy, but Serguei Korolev was a victim of Stalin.
About the B29; well, Yeager climbed down from the B29 to the X1 vehicle and it's intirely possible he had to move in open rarefied air to pass from one to the other.
Unless he had been sitting in the X1 all the time (like all tests made from B52's (X15 lifting bodies, etc...)