Headscratchers / Rigoletto

• Does the ending make sense in some way that I don't understand? One minute Sparafucile is talking about what a principled killer he is and that he does the job he's paid to do, and then he says he'll kill anyone who comes through the front door? Even if Maddelena talked him out of killing the Duke somehow, how does he think Rigoletto is going to react when he finds some random stranger in the sack instead of the Duke (never mind that it ends up being his own daughter)? Espcially when he's so concerned with getting the money for the job.
  • Sparafucile expected Rigoletto to just dump the bag containing the body inside into the river, without checking who is inside. It was by pure chance Rigoletto realised he was duped (by hearing the Duke’s singing). Also, Sparafucile tried to reason his treachery by the fact he did kill someone- just not the Duke.