Answer to Question 1
CFCs reach the stratosphere because they are very chemically stable. There the ultraviolet light breaks them apart, releasing the chlorine in them. The chlorine attaches to the oxygen in the ozone molecule, pulling it apart.
Answer to Question 2
A high glide blend has a large temperature difference between the bubble point and the dew point; as much as 10F. A low glide blend has a small temperature difference between the bubble point and the dew point; usually less than 2F.