Is the Almighty's saying, "Then We will not give them any weight on the Day of Resurrection" a metaphor for the baseness of their status and their punishment, and how do we reconcile it with the verses that affirm the weighing of deeds?

There is no contradiction between the weighing of deeds and the Almighty's saying: "And We will not establish for them on the Day of Resurrection any weight." The verse does not mean that they will not be weighed, but rather that they will be weighed, but their scale will not be heavy due to their insignificance and lack of good deeds, as Al-Shanqeeti mentioned.