Here are some things that you might be interested in thinking about.

Hyde is also a distrubing character because, though we know that he is evil, we never know what he actually does. Do we?! HE IS ALWAYS GOING TO OR COMING FROM SOMEWHERE. When he tramples the litte girl or when he kills the rich man (the only two “evils” we actually see) he is coming back from somewhere. Where does he go? What does he do? I think he’s a disturbing character partly because we don’t know what the evil, disturbing acts are. It is an empty space in the book, a gap in the text, and we have to imagine what Hyde is doing. This is a good technique for an author to use: the reader imagines whatever is “evil” and “disturbing” in their own minds. Every reader imagines their own horrible acts, and thinks about the “evil” side of themselves, and the “evil” acts they may desire to commit. Hyde is disturbing because he does whatever is disturbing in our own mind. He is the evil side of ourselves!
(Legend has it that Stevenson wrote a first draft (based on a nightmare) which described what Hyde actually did, and his wife read it and threw it in the fire! So he wrote it again, but without the “evil” bits. Sounds believable to me. It’s a shame we don’t have that first draft to read — then we’d know what “evil” stuff Stevenson fantasised about and maybe performed…)

Also, you mention Darwin and On the Origin of Species, but could say a bit more about it. It’s a good point that Hyde looks ape-like. I’d say a bit more about that. The important thing to do with Darwin and ideas of evolution though is about an idea called “degeneracy”. I’ve put the wikipedia link for Degeneracy in the sources box below, but it’s not too great so I’ll give you a quick outline. Degeneracy was the nineteenth century scientific theory that certain people were “less evolved” than others. It was a ****** and classist idea: it was basically the idea that people who looked like monkeys were closely related to monkeys… so black people and working class people were “less evolved”. This gave Victorian people an explanation for why there was crime and poverty – some people were just less evolved, so couldn’t be as “civilised”.
This idea is important in Dr. Jekyll and Mr. Hyde, because Hyde is almost the less-evolved side of Jekyll. Hyde is the link between Jekyll and his ape ancestors! This is why Hyde is always described as ape-like, and the reason why he is smaller. So Hyde, if you want to read it like this, is the “degenerate” side of Jekyll. Jekyll is civilised and scientific and intelligent, and he has to ignore and repress his uncivilised side – the side which just wants to act like an animal. So Hyde is disturbing in that he is meant to be the less evolved, degenerate side of Jekyll. This would be a scary idea for a Victorian reader — it would mean that inside every highly-evolved, civilised Victorian Gentleman was an evil, unevolved, monkey-like person. And so Victorian society might not be so “civilised”, “evolved” and secure as everyone thought — maybe there are Hydes inside all of us. (Jack the Ripper was the serial killer who popped up at about this time and scared people in much the same way — how could a doctor or a surgeon be an evil murderer?! He was meant to be civilised! The idea of an intelligent, civilised evil person didn’t make sense in those days.)
So Jekyll and Hyde might almost be about class war: between the good Victorian Gentleman and the evil, dirty member of the working class. Or a race war: between the scientific, civilized western world and the unevolved non-western world.

Good essay so far though. Hope this helped a bit, and good luck!