You are correct. しばらく for a while、経<た>った It(Time) passed ※経つ to pass(about time)、頃<ころ> time When it passed for a while since the situation cooled down＝a short while after the situation cooled down 事件のほとぼりが冷めてしばらく経った頃 When the public excitement of the case cooled down and passed for a while