Three things:
First of all, do the best that you can and don’t worry. You WILL get into a very good university, particularly if you can keep the A’s coming. You don’t have to go to U.Chicago to be a success in life. Most MIT and Stanford graduates are working for bosses and with coworkers who went to far less prestigious schools. In the US the prestige of the school that you go to does very little in terms of deciding what you do after graduation. There are a lot of good choices out there, and if you are strong in grades 10 through 12 many very good universities will be willing to overlook a bad grade 9.
Secondly, if you do want to go to a “top 40 in the world” university, and are willing to think about Canada, I am pretty sure that McGill does not consider grade 9 grades at all in the applications process. When they get your application they will recompute your GPA based solely on grades 10, 11, and 12 when available (assuming that you are applying during grade 12).
Also, most students who have literally straight A’s throughout high school still don’t get accepted to Stanford, Harvard or MIT, and I suspect that Chicago is probably the same.
“If feel like managing an A in much harder classes would at least show that I’ve grown since then.”
It will. I doubt that this will be enough for Harvard, Stanford, MIT, or Chicago, but it will be enough for many other very good universities.