Well, you already seem to be well on your way to doing the first thing I was about to suggest, which was to read as much as possible about the aspects of history which interest you most, and not to stick to school curricula. And, from the books you've listed, I'm beginning to sense a theme....

The one thing I would encourage you to do while you read all those books is to try to think critically as you read them: don't accept everything they tell you, try to follow the logic of their arguments and to spot inconsistencies or assumptions which they make. You're reading a mixture of primary and secondary works: that's great! But try to make sure you think really hard about the secondary stuff too; most of it is poetry and even Herodotus is not a 'historian' as we would think of one today. Always keep in mind that they all have an agenda when their writing, they all made conscious choices when writing to put one fact or another in or left other facts out.

Other than pursuing your critical reading, the other thing I'd suggest you do is to take as many languages as possible at school. I hated languages at high school, mainly due to awful teachers, but I really regret not putting in the effort early. I'm going to assume that your school doesn't offer Latin or Greek, but take Spanish, French, German and whatever else you can get your hands on. Once you've learned one language, and more importantly learned how languages work, you will find it much easier to learn the next one. So your Ancient Greek and Latin, which you'll need to learn if you want to become a professor of Ancient History, will come much easier in college.

Other than that, just keep reading everything you get your hands on, follow your interests, go down the rabbit hole, and enjoy it! I wish you the best of luck!

I'm a history major now, and the major form of preparation that predicts how well people in my major are doing is how well they learned to write in high school. What kind of historical writing does your school have you do? Do you learn to write about primary sources? Secondary sources?

What about in your other classes? How much do you write a week? Can you structure an argumentative essay clearly?

Don't worry too much about particular content-- just read whatever you're interested in. And while you do that, practice thinking about the argument in each book: what is the argument? How does it follow from the sources? Are you persuaded? What else might the author have done with those sources?

To be a professor is to ask for the privilege to focus on Research, Writing, and Teaching. These three form a cycle of learning, and all of them are equally important.

More pragmatically, to be a professor you have to have a PhD, preferably from a good competitive program (and prayfully, with full funding). To be admitted to a good competitive PhD program you have to show strong potential to do research and build a publication record. To best prepare for all these at the undergrad level you have to develop many skills, including analytical thinking, critical reasoning, good writing, and the capacity to learn and absorb knowledge.

At the risk of generalizing, one major issue that undergraduate students face is the ability to roughly speaking, get things done. They are used to being spoon-fed nuggets of knowledge and thus unable to put in non-trivial effort to learn something, analyze it, and then write it in good expository fashion. You see this in the very frequent "help me with my history homework" posts here and elsewhere on reddit. This is the kind of self-sabotage that can plague even graduate students. To earn a PhD in the US is simple: it requires that you make a novel contribution to a field of study. But to do so you have to first know the boundaries of what is known and unknown. And transitioning to this type of learning is truly not easy. The sooner you start, the better you will be.

Fortunately for you, /r/AskHistorians can be a very good tool for you to start to build those skills. Challenge yourself to contribute, in your domain of interest, within the acceptable level of quality. At the very least, use questions in your domain to challenge yourself to further your learning of the subject. This is what I use AH for and it's been really great for me. We have flairs who are in high school, yet they are very knowledgeable -- I'm certain we have top contributors who are in high school, too.

ACCEPT THIS CHALLENGE!