The monthly allowance appears to be on top of subsistence gardening, fishing, etc (recall Grandma Betsy from Chapter 1).
While the living conditions seem harsh by today's standards, they don't strike me as much different from those of poor whites in that era.
Note the monthly corn allowance, a southern dietary staple unwittingly responsible for the scourge of Pellagria http://www.eufic.org/article/en/artid/origins-maize-pellagra/
Good points. I remember reading about the experiment that proved pellagra was a B-vitamin deficiency.