Hi, this is PhD student from same country with you at 30ish school. I saw your another post at different website too. I hope I can help you with if possible.
I think you still have a chance to get in 30ish or even higher(cannot guarantee but worth to try). You did well in your masters and hopefully it can compensate your low undergraduate GPA.
Of course the student with high GPA from prestigious school will be the strong applicant, but other than that some schools give more weight to the name of school compared to high GPA, and other schools prefer high GPA even though they are not coming from top schools(at least okay school though). It depends on the admission committee of each school, but former case is my department based on examples I saw even though I'm from unknown school.
As Stat Assistant Professor already mentioned, I also recommend you to apply wide range of schools. Admission procedure has a lot of uncertainty. I know it would be costly, but you can spend that money for your dream. Besides the information from Stat Assistant Professor, I would like to say you can find the list of PhD student at each department's website, and you can see that they are favorable to korean or not. I know a few schools that they've (almost) never accepted korean.