I suggest having a read of the book Alcoholics Anonymous. Though originally published in 1939 it contains a wealth of useful information and it medical statements are remarkably close to todays medical thinking.
On question 2, if a person can their moderate they are not an alcoholic. It might be that a person has an event in their life that brings on a bout of alcoholic type drinking, but this passes when the event is resolved. Many folks have a drink when stressed but are not alcoholic.
4) The head of our national addiction service explained recently that an alcoholic of the hopeless variety (that's me) needs a "conversion" experience , which amounts to a complete change of ideas and thinking, in order to recover. AA uses spiritual means to acconmplish this, and throughout time isolated cases of spontaneous vital spiritual experience have been occuring, both bringing about recovery. So it does appear that a big change in attitude is required for long term recovery.