Dual citizen confused about how IBR works if I stay in America

I went to school in the US and am still here. But I grew up overseas and have dual citizenship in that other country, and really need some advice about how this works!

Am I correct in thinking that if I'm on IBR, once my repayment period kicks in, I will definitely start paying 10 to 15% of my income as long as I'm living and working in the US? But if I were to move overseas I could likely qualify for foreign earned income?

Sorry for the naive question, I've been reading through websites for hours and still don't fully understand it! I would like to stay in the US and want to factor in student loan repayments when applying for jobs. I have citizenship in the US and the other country.