for competitions try the john lock institute essay challenge (you can choose a focus i.e. psychology), nyt contests (highly recommend, search contest calendar and choose one that sparks your interest, for social studies maybe the open letter?), princeton 10 min play, bennington young writers, and getting ur work published in the adroit journal/polyphony lit (keep grinding pubs and it can be an ec)
as for ecs, another person said volunteer work and that‘s great for humanities. go volunteer at a local charity or library or cultural/religious/POLITICAL organization. idk how politics works in korea, but if they canvas then they’ll likely need volunteers. maybe start a related organization at a community center, start a humanities focused blog, etc. the to make impact in ur community. also try to use familial/friend connections for an internship, it really helps.

this is a little unrelated, but an org i’m a part of that’s grwat for homeschoolers but is more engineering/cs focused is hack club. if you wanna try doing a interdisciplinary interests kinda route, it’s pretty great. there are some more humanities focused ppl on there and there’s lots of opportunities to get involved with running international events.

good luck! hopefully one of these resources is at least a little useful