At this point, I'm not even sure if the Proteus make it to Duna, let alone back to Kerbin or Eeloo. I think they may have to use the Krussian space station to have any hope to get back, remember that that thing does have an engine on it, and aside from the hydrazine which can be purged simply by opening a window, holds the best bet for them to get back home or continue the mission.