We need to explain exactly how gravity is created.

It obviously comes from mass/energy somehow. From atoms, atoms are made of protons, electrons and neutrons. How do neutrons stick to protons if they aren't charged?
Extra mass is created when particles are joined together, how does this create gravity? What is mass really?

What more do we know about all the properties of atoms or quarks that can tell us something about what they really are?

"Gravity waves" have been detected. What more do we know about how gravity waves work. They travel at light speed, what else.