How do the views of Helen and Marius on faith and spirituality differ? How are faith and spirituality represented in the play, and how does Elsa's dismissal of spiritual matters factor into this?
Let's do Marius first. His faith and spirituality are Judeo-Christian. He believes that there is one way to achieve salvation and everlasting life: by grace through faith in Jesus Christ. He believes that there is evil and darkness in the world, and the way to fight it is by believing in God the Father and the saving grace of Jesus Christ. Along with all of that would come church attendance (he is a pastor, remember) and worshiping within a body of believers.
Helen used to support Marius's faith and spirituality, but she rejected it many years before the play takes place. Like Marius, Helen does believe in the presence and power of evil and darkness. Contrary to Marius, though, she believes that her artistic creativity and expression can fight the darkness and bring her to spiritual rightness and salvation. To Helen, her creative expressions both actually and metaphorically fight the darkness. Metaphorically her art helps keep her spiritually intact. It gives her comfort and peace. Her art actually brings light to her home, too, since much of her indoor creations involve using candles and mirrors to illuminate as much of her home as possible.
Last is Elsa. Your question mentions that she dismisses spiritual matters. I don't see that in the character. I don't see her dismissing spiritual matters at all. She doesn't tell Helen that her beliefs are stupid, and she doesn't outright dismiss Marius's beliefs either. Elsa simply supports Helen versus supporting Marius. Elsa believes that if Helen's chosen spirituality brings her comfort and peace, then it is right for her. If Marius's faith does the same for him, then it is right for him. Elsa has a spirituality in my opinion. It's akin to the New Age movement in which spiritual salvation can be achieved through all kinds of avenues. All religions and beliefs can be right at the same time, because it's what's right for a particular person. That's how I see Elsa.