What are my chances of being accepted to Harvard as an undergraduate?

I am an international student from South Korea, currently attending an international school in South Korea.
I have 1550 on New SAT, 800 for Math 2, 800 for World History, and 790 for Literature.
Our school is an IB school, so I have gotten into a full IB-Diploma Program.
I have taken: English A HL, History HL, Korean A HL, Theatre HL, Chemistry SL, and Mathematics SL. On the IB exams, I have gotten all 7’s except for English, which I got a 6.
Speaking of extracurriculars, I have served as a member of Student Council for 4 years — Vice in my junior year, and President in my senior year for the Student Council Chair(meaning for the whole high school, not just a grade).
I have founded Make A Wish Club, in collaboration with Make A Wish Korea, and have made 20 wishes of children with severe illnesses as a club(examples of wishes were getting a macbook, meeting a K-pop star, etcetera. All money collected through fundraising).
I have participated in various drama productions, including musicals which I have always gotten lead roles, and I was nearly scouted by an actors agency with my performance. I am also a part of teen theatre group outside of school, which is a group of young international aspiring actors and actresses. Plus, I have participated in this project called dream theatre – we would visit an orphanage, and work on a play with the children there, and eventually perform in front of a large group of audience.
I have a great interest in writing. I have been in a publication class of my school since freshmen year, becoming the editor-in-chief in my junior year. I have also written in a magazine called Teen 10 Magazine(magazine for English speaking teenagers in Korea), and served as a Editor-in-chief since my sophomore year. For my personal project, I have written a 200 page novel, which was published in Korea, and have won a literature award in Korea in an international section(since it was written in English).
I have been in JV basketball team in my freshman year, and Varsity since sophomore year, and have become the captain in my senior year.
I have worked with Save the Children Korea for all 4 years in my high school, volunteering there during every school breaks. I was a translator – translating letters from the sponsored children into the Korean sponsors(English to Korean).
Since my sophomore year, I have worked as a staff member in professional musical and play sets, and also worked as a tour guide for foreigners staying in this youth hostel, travelling with them all around Seoul.

I have written my essay, and received recommendation letters from my counselor, newspaper teacher, and history teacher.

How are my chances?

Definitely some great ECs. What I get out of wht you have said is that you want to do something in English/Journalism and are a philanthropic person. If that is true and the major you applied to is related, would say you have a pretty good shot (so long as your converted GPA is up to scale with your great SAT score). However, if you applied to something like Bio, it might raise an alarm in the eyes of the admissions office, as there aren’t any extracurricular activities supporting that interest. Just make sure you have some good essays that say things about you. They want to know your character (as well as your writing abilities), not credentials that you have already provided. Good luck! If you really want Harvard, I would recommend applying ED/EA!

Harvard is a lottery school and a Reach for every applicant and even more so for an International applicant. You look like a competitive applicant so all you can do is apply and hope for the best.

Good Luck.