The Aether density analogy was something Aaron Murakami suggested in his book "The Quantum Key.
" In fact, he mentions density twenty-six times while discussing the Aether's gravitational effects. But, again, it's just an analogy. A shortcut for expressing relative numbers of force lines interacting within a given region of space. Pressure differentials.
For example, when you said:
Look here at these two galaxy's which look far into the process of merging. The original shape of each galaxy is lost. Nothing holds it together other then the way mass was distributed when it formed.
I did not agree with your description, but rather than be smug or dismissive, I decided to suggest a different approach.. which hasn't worked out any better, but such is life.
Those two galaxies appear to be "holding together" as well as is to be expected while tearing each other apart or "merging." Sawing each other to bits. This is just a multi-body problem to solve in classical (Newtonian) physics. Each galaxy being comprised of possibly millions of masses, each with its own orbit, tilt, and spin making for a zillion equations to solve for a zillion unknowns.
But we can greatly simplify by asking practical questions instead of demanding an equation telling us everything possible at once. How fast are the two galaxies revolving around each other? How fast are they approaching one another? What's the apparent mass of each galaxy? Combined? And so forth.. With a few such answers we can predict how the picture will likely change well enough for our near term purposes.. with no discussion of the Aether at all.
What Ken Wheeler bangs on about is the fact that multiples of such bodies or masses (whether they be stars, galaxies, black holes, or whatever) are not attracted to each other as Newton's famous equation has commonly led us to believe. All individual masses are actually attracted toward their instantaneous collective center of mass. So even when considering only two masses of equal weight, their gravitational force vectors will point toward some spot between them, but not necessarily toward each other's center of gravity.
Say they're egg shaped and spinning..