fixing ideas on dark matter and other cosmos stuff

These question and answers are from between Dr. Cheng and myself. Of
course, I'm asking questions and he's answering after the ***. I had
the complete wrong idea about dark matter....oops.

First, if dark matter is attributed to the expansion of the universe
and dark energy is attributed with an accelerating universe via the
cosmological constant, then how are they not directly related?
***Dark matter, just like ordinary matter, is subject to gravitational
attraction, while dark energy, to gravitational REPULSION. In our
universe there are (4%) ordinary matter/energy (called baryonic matter),
(21%) dark matter and (75%) dark energy. So dark matter and dark energy
are NOT, under our present understanding, "directly related".

Second, what are the chances that the expansion is not due to vacuum
energy? Kari said that some have tried pinning expansion to vacuum
energy, but that the vacuum energy is orders of magnitude less than
what is needed to achieve what we observe. However, would this vacuum
energy need to be handled as nonuniform if one considers that space is
warped? Whoever looked into this, how did they handle consideration
of vacuum energy? Does it even change according to the warped-ness of
space? (pardon the layered questions)
*** Cosmological constant is the name of the math term in Einstein's
equation that has the effect of being gravitational repulsive. Its most
probable PHYSICAL interpretation: "it's the energy of the vacuum". But a
straightforward calculation shows that the quantum mechanical vacuum
energy is 120 orders of magnitude too large compared to the observed
amount of dark energy (NOT too small). If it is the cosmological
constant, the warped-ness of spacetime will not bring any nonuniformity
in dark energy.

Third, I read somewhere that there are drag effects of objects
orbiting in space. Could a more fluid-like consideration of space
give rise to the expanding universe (high/low pressure systems
depending on empty/filled space or rotating vortices)?
*** Yes a rotating gravitational source can drag the spacetime around
it. But all this is consistently accounted for in the context of general
relativistic description of the expanding universe.

Lastly, is dark matter thought to exist as a constant amount; if not,
where might it come from?
*** Dark matter is definitely not uniform. In fact the present
understanding of the observed cosmological structure (galaxies, clusters
of galaxies, voids...) is built on the idea that structure formation
started among the dark matter first (from gravitational clumping), then
the baryonic matter falls into the grav. Potential wells formed by dark
matter. The favored idea of the origin is that they are the cosmological
thermal relics (just like the cosmological microwave background
radiation).