If you have gone to new atlantis, you already grav jumped (so if you have a mission you probably have done it). Grav jumping is just when you go to another system from the map interface (for example, from alfa centauri to sol). If the place you want to go to is too far, you just need to do intermediate jumps (going to systems in betwern)

Nay, I don't really see any problem woth their content or posts. Not that I agree with what they say and some of their communities, but for example their games community has interesting content.

You can chaim grav jumps, only thing is you cant do the entire trip in one jump. Fuel resets each time you jump, so ot's only a minor inconvenience to start with.