Councillor's wife questline is there to make Evelyn flee, and the whole mysterious murder is simply leading you to Braccus Rex. since you basically finished the Braccus questline, there's no need for Councillor's wife quest to finish.
also, the op didn't mention entering Evelyn's lair. afair, you can only enter her lair after obtaining her diary. if in the op's case, Evelyn hasn't been killed, but Zombie Jack assumes that she was dead. then the game simply determines that the amulet is gotten by killing Evelyn.
