To address the part about temperature and pressure, these are engineering considerations, based on what can practically be achieved. In general, liquids have rather small variations in density, so standard reference values are usually good enough for a wide range of rocket configurations.
What would the bulk density of the LOX be? I have so far assumed 1,141 kg/L. However, this needs to be at a pressure higher than atmospheric pressure, correct? Or at a very low temp.
Yes. High pressure is impractical, since pressure vessels are heavy. That would cause the dry weight of the rocket to be much higher, decreasing performance. So the pressure is close to atmospheric for practical reasons. Instead low temperatures are used, typically a little below the boiling point in order to be able to have the rocket stand by for a little while before the propellant boils off.
In this case, then what is the density of the fuel? Meaning, how do we select the P and T at which the density of the kero should be determined?
The same pressure argument exist here. To compress the liquid for a very slightly better density, the container must be much stronger and heavier. A small boost in kerosene density can be achieved by chilling it down slightly, but this is limited by the freezing point of kerosene. You can't pump solids, another engineering concern.
And would T and P other than standard conditions affect the O/F ratio, rw?
The intake condition of the propellants could affect their rate of reaction somewhat, causing the engine to have a different optimal O/F ratio.