What are things that Holden loves? I have: Phoebe, Allie, museums, and reading..what am I missing?

Holden definitely loves all the things mentioned here in your question. Three more things that he loves are authenticity, or the opposite of phoniness, innocence, which he observes most often in children, and writing, which is a way for Holden to connect with language and the literature he loves to read.
Holden's chief complaint throughout the novel is about phonies. These kinds of people irritate him to no end. His appreciation of and his tireless search for authentic interactions and unselfconscious truthfulness likely link to his admiration of children. In their innocence, children can't help but say what they think and be exactly who they are, which are qualities Holden looks for in his peers and in the adults in his life.
Holden's love for writing and language are clear in his willingness to work for his English teachers so he can actually pass, as well as in his prodigious appetite for conversation. As well, Holden is willing to write an essay for Stradlater to pass off as his own, which most students would not be happy to do.