How many times can you be wrong? Let me count the ways.
1) In "my" ball model, down is actually towards the center of the ball.
2) What is the law of density? This looks like a "flat-earth" fabrication of a law that never existed. If not, what is the formula for the law of density that perfectly describes the physics of falling objects that makes Newton's formulas superfluous?
3) The law of buoyancy is a function of the weight of the fluid displaced by an object immersed in that fluid. The weight of the fluid is a function of --- gravity.
4) What is the density of the sun and the moon, and medium it is placed in? If "it is a fact that objects placed in denser mediums rise up while objects placed in less dense mediums sink down", then shouldn't these "objects placed in less dense mediums sink down"? Are the sun and the moon less dense than the atmosphere at 3000 miles?
5) Bouyancy and Density is a demonstration of the effect of gravity. Newton's formulas with gravity not only accurately explain everyday physical observations on Earth, but the same formulas accurately describe every observations of planetary orbits. Laws of density and buoyancy, without gravity, do not. These laws of density and buoyancy provide less than perfect explanations than Newtons law of gravity.
6) "Not a single experiment in history"?!? In all of history, countless experiments and every day observations demonstrate over and over the same gravitational attraction according to Newton's equations. In 1997, the "NEAR Shoemaker" satellite was attracted by the mass of a nearby asteroid "253 Mathilde". In 1998, a failed Asiasat 3 satellite was sent around the moon, using the moon's gravity to produce a better orbit. Today scientists can measure the force of gravity with an atom interferometer. You can perform your own experiment from home:
www.pasco.com/prodCatalog/EX/EX-5550_universal-gravitational-constant-experiment/index.cfm
One you got partly right:
1) If you dig a hole from UK to Australia, and fell through feet first to the other side, you would be upside down the instant you pass through the center of the earth.
I'm wide awake.