Thank you for this post. It seems that Insassen were supplied adequate food (obviously not wine and beer). All genuine reports say the same story, that the Kapos stole food for their own gains at the expense of others. This activity still occurs today in modern prisons. The diet was exactly the same or more than the Wehrmacht soldiers got. German civilians got less which could account for the total grumpiness of the Gestapo etc in the latter times.
I checked the menu given by the Wehmacht soldier Wolfram against the French Monowitz inmate Sam Pivnik and also Alex Kurzem; none of them like the food of course but it was identical. I don't mind the cops getting slightly less
The real issue was the black market, this is from all accounts which the Gestapo were not authorized to investigate; Kripo were ineffectual or so hungry they were involved, this is and should be the next source of investigation.