Ok you may be stranded but clearly you can live off the plants there. Also assuming hyperspace technology does exist in the other side and the mapping information is in the ring - this means getting back is highly dependent on beating Thrawn and Baylon which means have a sizeable force greatly improve your fighting chance. Which makes not taking whatever fighting resources with you even more stupid as seeing you are taking all the whales on a one way suicide trip already.
Also it appears the nightsister has significant presence in the other galaxy and would have star maps and navigation data for that galaxy as well as the return navigational information as they made the trip first place millenia ago. So it won’t be difficult to say that planet has all the resources for the ships to return back to the story galaxy. Which makes the whole series fall apart, as Thrawn would have the resources to return to the story galaxy. Nightsister has the nav data which he appears to be in league with, hyperspace tech in his star destroyer, fuel for hyperspace clearly exists in the galaxy.