It would be hard to eat. But until Harry rescues him (or rather, stumbles in and breaks the wards), Draco's in a room that magically sustains him. No need for food or water, or even air.

He does have some memories; he still recognizes Harry. What's missing are many specific memories of his past and what he went through.

As for why else flippers...let's just say that the Unspeakables are using the horror Draco would feel at his own mutilation to power some of their magic. This is really not a nice story.