The Question and Answer section for A Farewell to Arms is a great resource to ask questions, find answers, and discuss the novel.
Catherine explains her fear of the rain in the following way;
"'...sometimes I see me dead in it...And sometimes I see you dead in it.'"
I need to look further for the information about Frederic.
Yes, this novel is a "study in doom" because Hemingway has a sick twist for his characters. It appears that Heingway is intentioannly setting up his characters for a terrible ending.
When asked why he got involved in the war, Henry says, "I was in Italy, and I spoke Italian."