Liquid Oxygen Questions

I'm puzzled by two inter-related questions regarding the atmosphere
of a habitat.

First, if we assume an atmospheric pressure, could be anything, but
let's work with 1 atmosphere. The effect of this atmospheric
pressure would be to exert a force of 15 lbs/in2 against the
pressure vessel. Now how does the radius of the cylinderical habitat
effect the total mass of the atmospheric gases? The way I see it,
the mass of the gases is directly proportional to the area of the
pressure vessel and the height has no effect. If this is true, is
there anyone in this group who can address the question of at what
height would the atmosphere be so thin as to not be life sustaining?
I would think that the majority of the atmospheric mass would be
concentrated at the highest gravity gradient. Is that correct? Or
could it be that the gases, while still maintaining the same 15
lb/in2 density are more evenly distributed and therefore, would be
thinner that what we would expect on the living surface but thicker
at higher altitudes?

Second question, how much volume of oxygen can be compressed when it
is in liquid state? 10:1; 100:1; 1,000:1? How much energy is
required to maintain the liquid state, if the oxygen storage vessel
is floating in space? Same question, probably more important, for
the nitrogen content. Afterall, it'll be a big component too.

In a nutshell, when we are processing lunar/asteroidal material at a
SMF, and oxygen/nitrogen are by-product gases, which we'll be
storing for eventual use as the atmosphere, how large will those
storage vessels be. For the sake or argument, lets say the volume of
the cylindrical habitat is .5 KM radius and 5 km length, and the
endcaps are flat, rather than spherical (just to make the volume
calculation easier.)

This could lead into an interesting discussion on the stages of how
to build a habitat and how early the atmosphere can be introduced
while other exterior/interior work is progressing. I'm assuming that
the sooner we can pressuize the habitat, the less gas storage
vessels we'll require. I'm also assuming, that we won't want to vent
the gases while constructing the habitat and thereafter concentrate
on filling it with an atmosphere. That doesn't make sense to me.