Hey abhi, I am from india too ! and i got 890 and am applying to astro too. I guess your list is just fine ! if i where you , i would try increasing the number of schools you are applying to, like say to 7-8. i have quite similar profile but from a engineering background. you could aim a bit higher.
Try considering Yale astro, chicago astro and Washington st. has a pretty good astro group too. these may be a good list of ambi for you as you have good PGRE score. especially if your projects are related astro, there is really a good chance you would get into these schools.