Folk and acoustic: I know what folk is in terms of song and music - acoustic defines as 'pertaining to sound' - which surely all music, whatever variety, does. However, am happy to accept F & A as a warning not to bother as it takes away any chance of choosing what I listen to (not keen on C&W, Wagner, hip-hop, garage, punk......)
If you think that turning a club over to non or bad singers is going to attract audiences (other than those who prefer non and bad singers) - we move in different circles. Practice before you go public, not in public. What do you do if, as one singer improves having practiced at your club, another bad singer comes along - ad infinitum? There are many ways to learn how to perform, but NEVER in front of an audience.
Landfill as far as I used it, refers to not giving the audience what you have promised but running a 'song' club rather than a 'folk' club; standards is a different question altogether.
As an ex-teacher you will be aware how self conciously frightened young people are of making a fool of themselves in front of strangers, especially a large number of them - it only takes one song to fall apart and you won't see them for dust - seen it happen.
Why are people so insistent that encouraging aspiring singers with help and advice rather than throwing them in at the deep end and watching them flounder, is abandoning them?
If I had been a casual individual interested in finding out what folk song was and had visited a club where you were "playing wrong chords, forgetting words and sounding really awful", I certainly wouldn't have come back. Did you expect the other singers at the club to pick up the pieces after you had made a fool of yourself and was the extra work you put them through worth it now you have "had your first professional booking"?   
Jim Carroll