Hi,
I think you have a very good profile. Prior research experience is desired for PhD which you have. I believe you can get into Ivy leagues with 1500+ score.
For GPA conversion, you can ask your prof to write in LOR that you are in top 1% of students. Also, if you have specific universities in your mind, you can see your chances of admission at www.missiongre.com . Use the form to see your profile strength. Taking subject GRE can also increase your chances of getting in top univ.