Helium baloon is the proof of your so called gravitons are absent.
No. Helium and bouyancy in general is a disproof of the air causing things to fall.
If air caused things to fall, the helium filled balloon should fall as well.
The only explanation for the buoyant force is the air (or whatever medium the object is in) pushing objects up.
The buoyant force is measurable and acts on all objects.
All you need to do is measure the weight of the object in a vacuum and then measure it in air.
You can also easily observe it with water.
Fill a balloon with air and watch it fall, but put it under water and you can watch it rise.
You can even fill a balloon with helium and watch it rise in air, but sink in hydrogen or low enough pressure air.
So it is clear that the helium doesn't push itself up, instead the air around it does.
The only sane explanation is that there is a general downwards force acting on all objects and a medium applies an upwards, buoyant, force on objects immersed in it.
This ties into the pressure gradient of the fluid caused by this general downwards force as this pressure gradient is what causes the upwards force.
This also shows that the air is pushing objects upwards, not down.