- Then Luke somehow conveniently finds part of Leia’s message while cleaning R2
Of your complaints, this is the only one that is a plot convenience. Having one or two of these at the beginning of a story is very standard. The audience usually has no problem with it as long as the storyteller doesn’t make it obviously absurd. The idea to have Luke clean dirt out of R2 and then jar the message out of his memory is a very subtle way to get the story started.
I always thought that R2 had intentionally played the snippet of Leia’s message as a way to trick Luke into removing the restraining bolt?