It DOES make sense for Superman to have large muscles, actually, because he was a football star in high school before his powers fully developed.
a) Not anymore; Johns brought back Superbaby. b) Muscle growth is not permanent. It must be maintained. He'd lose his figure within a year of getting his power.
And no amount of lifting oranges will give you a figure like Clark's. At the very, very best, he'd look like an ordinary, reasonably fit white collar schlub who's never seen the inside of a gym but usually takes the stairs instead of the elevator. In other words, not remotely heroic, not even as built as Wally, nothing like the tank he needs to be to look like SUPERMAN in modern comics' visual language.
I don't think Diana CAN jerk the moon out of orbit
If three people can jerk the Earth out of orbit (JLA: Obsidian Age), any one of those people can jerk the moon out of orbit. (Also, Clark was seen to be able to *destroy* the moon in a recent McDuffie JLA, which would require considerably more strength than moving it.)