problem seems to me, that you will have a statistical distribution of amide, diamide and non-reacted aniline by the end of you process.
I would start by removing all voilatile material, i.e. "drying"
the residue I would wash with slightly HCl - acidified water ./. DEE (removal of TEA as hydrochloride, removal of excess aniline ) . higher amounts of suberic acid might be insoluble in both layers, so filtration might be necessary / a good idea
the etheric layer then should consist of amide, diamide and suberic acid in etheric solution
as I expect the solubility of the suberic acid to be significantly higher ( 2,5 g/L , 20°C) than the respective solubility of the monoamide, I would wash with water once or twice
by now, it depends: KOH/water ? might form a soap and spoil the party, or might work and allow for separation from the diamide - you'll have to test for that
anyway, recrystallisation or chromatographic workup looks like the final step to me