Points about question 3, 4 and 5.

3.  It is correct that physicists do not understand the nature of
quantum gravity (really at all).  Basically, quantum gravity represents
the union between the principles of quantum mechanics (which is a probabilistic
description of the state of matter) and general relavity (which describes
the behavior of gravity as curved space time).  Now, when the Universe is 
very small it is essentially in a quantum state and gravity must be
described differently.  The fact that we have no real understanding of this
means that we don't really know the physics of the very early universe - at all!


4.  If the baryon density is high then deuterium will easily fuse with another proton to make 3He thus destroying the deuterium.  If the baryon density is low then most of the deuterium will be photo-dissociated (by the high energy photons) before making 3He.  A high baryon density Universe means a low density of deuterium (and a high density of helium)  A low density Universe means a low density of helium because most of the deuterium is destroyed before it can be fused into helium.  Since deuterium is destroyed in stars and monotonically decreases from it’s primordial value, deuterium is an important probe of the baryon content and the early universe.

 5. Galaxy 1:

Z=(7220-6563)/6563=0.1

V=300000 x 0.1=30000km/s

Galaxy 2:

Z=(6556-6563)/6563=-0.001

V=-0.001x 300000=-300 km/s

a redshift can be negative - this can occur when two galaxies are sufficiently
close such that their mutual gravity overcomes the relative expansion between
them and they attract one another.  This actually is the case between our
galaxy and the Andromeda galaxy.