Re: How does Freon 12 travel to the ozone layer.

Your question is quite a complicated one. Let me go through it point by 
point.

A molecule of freon is a lot heavier than a molecule of oxygen or nitrogen,
but it is still a million times or more lighter than a dust particle, a
crystallite of salt, or an ice crystal. Rates of gravitational separation 
of different molecules are minute compared with the rates of various air 
currents that carry particles all over the place through the atmosphere.
You know well how smoke particles, clouds, dust are held aloft in the 
atmosphere for long periods and carried to great heights. How much easier 
for freon molecules, which are a million times lighter!
There is a bit of double-think on the part of the anti-scientific lobby, 
who try to tell us on the one hand that freon molecules can not get to the 
stratosphere, and on the other hand that salt particles can do so in great
quantities.

Your understanding of the process is generally pretty right. But it is free
chlorine atoms and not chloride ions that are formed. This is important,
because chlorine atoms are very reactive free radical species. Chloride
ions, on the other hand, are unreactive, and have a high affinity for water.
Moreover, chloride ions do not exist in the gas phase in the sort of
conditions that prevail in the stratosphere, but only in crystallites, or 
in droplets of water or acid.
But you are correct in supposing that in order to get to the destructive
radiation, freons must rise above some of the ozone layer that is filtering
it out -- a height of 30 km or so.

Your next question is how the freon gets up there in sufficient quantities.
This is the point of the whole danger of CFCs. There is almost nothing else 
that can happen to them! So that although only 1% of the freon gets up there
each year, the other 99% accumulates in the lower atmosphere, ready to get 
up there later on. By now, there is the equivalent of about 30 years' world 
production of freons at 1980 levels in the atmosphere. So 1% of that decaying 
each year amounts to about 30% of a year's production at 1980 levels.
The other important point is that the ozone destruction mechanism involves
a catalytic chain reaction, so that a single free chlorine atom can destroy
several hundred ozone molecules, so it doesn't take as much atomic chlorine
as you might expect.

You ask for a comparison of freon with other sources of stratospheric active
chlorine. A rough breakdown is freons about 45-60%, other anthropogenic 
compounds (HCFCs, methyl chloroform, methyl chloride, carbon tetrachloride)
about 25-30%, natural methyl chloride (from ocean biota and biomass burning)
about 10-20%, volcanoes and salt spray near 0% -- definitely less than 10%.

There is access to a lot of good information on stratospheric ozone via the
links at SOLIS.

If you can get hold of the WMO report "WMO Global Ozone Research and 
Monitoring Project —Report No. 37: Scientific Assessment of Ozone 
Depletion: 1994." it contains a lot of the information you are looking for,
and has a very readable and accessible introduction. There is a more
recent one too, but that is the one I tend to use.

There have been direct measurements of freon levels in the stratosphere
since 1975. Here are references to the very first ones: Schmeltekopf, P.D., 
et al., Geophys. Res. Lett. 2(1975), 393-396, and Heidt, L.E. et al., 
Geophys. Res. Lett. 2(1975), 445-447.
The amount of salt spray in the stratosphere has also been directly 
measured. It is much smaller. See, for example, J.C. Delaney et al., J.
Geophys. Res. Issue of December 20 1974.
In both cases there are, no doubt, better more recent measurements; I happen
to have these to hand because I have been able to lift them from my wife's
historical researches!