Chemistry isn't a sub-field of Physics either.
Chemistry is just applied Physics.
And yes, for all you mathematicians out there, Physics is just applied math. :)
Oh but it does. (The force of gravity is essential for some (al)chemical techniques.)
He literally coined the term when talking about his movement. If anyone has claim to what the definition was, it's him.
But history is written by the winners and I'm sure modern day fascists would like to distance themselves from that history as much as possible...and thus the term gets narrowed and redefined.
No, but it does make it part of "Newtonism."
Sure, but that doesn't mean any one aspect of what he did, in isolation from the rest, is "the definition of fascism". (And the understanding of the genericized term is at least as much shaped by Naziism as Italian fascism, anyhow; this might annoy Mussolini if he was around to be annoyed -- frankly, that Nazis are taken as an example of "fascism" would probably annoy Hitler, too -- but, you know, that's just the way language evolves; if we're talking about Mussolini's movement in Italy specifically, we generally say "Italian fascism", not just "fascism" unless there is context to indicate that we are specifically talking about Italy.)