Maybe...... If you use "epiphany" as a feeling, You can say " 감(感) 잡았어" when you realize or comprehend the essence or meaning of something.

"너 때문에" is correct in this sentense, " I didnt come here for you..I came here for myself." If you translate this sentense "There is a present for you.", you can "저기에 너를 위한 선물 있어" As you know, "for" have a lot of meanings. I think that the difference depens on the "for" 's meaning.

I think you means "주관이 뚜렷한" in Korean. We, Korean, used the expression to explain someone who has his/her own beliefs, styles and values about doing, thinking, deciding, etc.... When you introduce your presonality on your resume or for interviews, you can say "저는 주관이 뚜렷합니다." or "저는 주관이 뚜렷한 성격을 가지고 있습니다." in a good way... If you have too excessively "주관이 뚜렷한" personality, it can be "고집이 센", which means stubborn or obstinate. I hope my description will be helpful for you...