Build the equipment! Make a hermetic pot of cadmium, evacuate it, heat it to 250°C, introduce your chloride slowly to less than 1Pa. But why your amines wouldn't mess with the rest at that point is very obscure to me.
OK, you don't want to experiment that, right?
Would it be possible to swap the roles of the chlorines and amines in your phenyl? The -Cl can be replaced by -NH2 (can't they?) so you might perhaps make the couplings at the original -NH2 instead, before or after transforming the Cl. Either use the -NH2 directly, or transform them before into -NO2, -OH, -Br... Would that make any sense? (And apologies if not)