I think you are making it more complicated that it is. It's pretty clear that gravity and mass are closely related. That doesn't mean there are not other things that affect gravity or things in the universe that are not fully understood. In my observation, most scientists aren't trying to conspire to hide the truth, they are just trying to figure out how things work. Don't confuse that with how politicians sometimes portray the science (not that I've seen a lot of that in terms of gravity). Figuring out the mechanics of how the Universe works in itself doesn't really say anything about the existence of God. Pretending we can understand absolutely everything there is to know about the universe is the height of hubris. However, that doesn't mean we can't always learn more. It's just that there is always more to learn.
If we didn't have a pretty good approximation of how gravity works, we wouldn't be able to orbit satellites. The calculations that are used for that are based on mass. Unless you think the existence of satellites is a conspiracy.
Also, things "defy" gravity by using some kind of counteracting force (e.g. airplanes use the pressure difference created by the shape of the wing to create lift). "Lifters" do the same thing (that is use a force to counteract gravity, not use lift the same way an airplane does): https://hackaday.com/2016/07/13/expanding-horizons-with-the-ion-propelled-lifter/#:~:text=High%20voltage%20is%20applied%20between,explanation%20of%20how%20it%20works.
I appreciate your well stated points.
Thanks!