Since our dog died, my father has become a shell of his former self.
この場合、次のような言い方ができますよ。
ーSince our dog died, my father has become a shell of his former self.
「愛犬が死んでから、父は魂を抜かれたようになっている」
to become a shell of one's former self で「魂が抜かれたようになる」を表現できます。
ご参考まで！
カナダ 
