I don't think this is accepted by mainstream science. It might be your theory, but I don't believe it's widely accepted, or that it has any proof.
No proof of floating in space (or space itself, for that matter). NASA underwater pool walks and green-screen astro-not actor-batics excluded, obviously.
Nothing to do with Heliocentric gravity. Density and buoyancy are accepted by Flat Earth, provided gravity only acts downward, as observed.
This is all Heliocentric theory. I can make up a similar theory about the Heliocentric pixies which are the real reason for our observations. One can't use a theory to prove itself. Using Occam's razor, we don't need Heliocentric theory at all. Earth is flat, and stationary, just like the bible states.
Theory again. No proof.
As above. You can't use heliocentric assumptions and theory to disprove flat earth. Flat Earth doesn't require these superfluous beliefs or unproven assumptions.
Huh? Again, I think you're using Heliocentric theory to try to refute Flat Earth. Venus and Mercury are simply wandering stars, traveling in the firmament around the Earth. They're not between Earth and the Sun anymore than any of the other stars. Happy to explore this point further - I'm not an expert in the movements of the Heavenly bodies, but we don't need to be to observe that Earth has no measurable curvature, nor observable or detectable motion.