What's the GPA scale in Sri Lanka? 2.5/4 in the US is not good, but I don't know about there. Admissions committees might not know either.
80% is a very good score for the subject GRE, and is roughly what top-10 grad programs expect. However, that may be for domestic applicants: I've heard that they expect better GRE scores for international students.
Another question is which graduate programs you want to get into. There are rather a lot.