It took a while, but the Rust version of the code generating the positions of galaxies has finally reached the level of functionality of the C version. Meanwhile, I have gathered quite a bit of interesting experience, which I'm now going to share.
Rust vs other languages
Programming in Rust is nothing like programming in any other language I've had contact with (which means mainly the C family and Python). One remotely similar experience was experimenting with Haskell, but even that generally due to incompatibility between my intuition and the language (although Rust has many functional features, but as will be mentioned later, one shouldn't overuse them...).