I definitely agree that reality may not be as it appears and that in many cases it is stranger than fiction. Several of my posts discuss how reality largely exists as an illusion created by our mind.
I also agree that I haven't seen "the ball" with my own eyes. So for me to believe that the earth is a sphere, I need to believe in the validation of others. I need to believe in gravity and that the pictures of earth that are taken from satellites and telescopes, which show that the earth is round, are real. I also need to believe in a lot of other science concepts that I myself cannot prove. In order to believe that the earth is flat I also have to believe that all science is a lie and that it has not progressed at all since the 1500's.
If I am to only believe in things that I can directly see myself then I am severely limited to what I should believe in. For instance, I cannot believe in atoms, viruses, bacteria or oxygen and so on. So with that in mind, if I cannot validate that the earth is a sphere or flat then I should not believe in either. Really, why believe in anything?
Regarding gravity and your statement "what if we’re simply motionless and things fall to base level because they're heavier than air." I find this confusing because weight (heavier/lighter) is a product of gravity so if we are motionless and there is no gravity why would a heavier object fall to the earth at all? In that scenario everything should float, which it does not.
Gravity easily explains why earth is a sphere. Gravity pulls all objects toward its center without direction (up or down) and by an equal force. This creates a symmetrical sphere shaped object. Disc theory and gravity cannot coexist because the pull of gravity towards the center would make earth collapse under its own weight, just like when you hold a piece of paper in the middle and it collapses under its own weight.
Flat earth theory for me simply isn't parsimonious. It requires too much work to make sense (ie. believing in crazy pseudo-scientific explanations, believing that everything is a lie, believing that all science is a conspiracy). Its not even worth it. I may as well just not believe anything.
If gravity doesn't exist, how can weight be a product of gravity? Wouldn't it just be the mass and density determining the weight and only air resistance to block the way for the object to drop to ground level? Not sure if that makes sense, but I'm playing with the thought for the sake of the argument.
I completely agree that the theory requires some work to get around the common consensus.