hanseul

I'd say your acceptance won't likely hinge on the GRE, particularly with thise scores, so if you have limited time in preparing your applications, you might be better of focusing on other areas. Most admissions offices understand non-native speakers will be less competitive on verbal and awa, so given your area of interest I'd say you're probably fine gre-wise. 
That said, if you want to do it for personal satisfaction/peace of mind, that's another question entirely. 

If the difference between getting into a top-10 program and a top-20 program is one month of GRE prep, I would do it. Or if the difference between getting into a program with better funding lies in a better GRE grade, I'd still do it. And you seem quite confident about a significant improvement in your grades, so makes all the more sense, especially if you can up your AWA a bit.