Cool poster! Though I think dark energy (and possibly dark matter) will be seen by future generations like we see luminiferous ether or epicycles today.
Agreed, I think the same. We just don't know what that stuff is yet. It could be a bunch of different things we haven't discovered because we can't measure it yet. Who knows. Fun to think about.
Gravity is not the only basic component of the universe. What they are saying is that dark energy pushes things apart. It behaves in the opposite manner of the gravity we are familiar with.