Is there a theme that relates to friendship, heroism, or prejudice?

Sure, those are some of the major themes in the book. I think that you could do at least a separate paragraph on each. They are, however, separate themes. It would be difficult to lump them into one. The relationship between the main characters (friendship) is different than the prejudice which exists between the Greasers and the Socs. The Heroism shown by Pony and Johnny in the burning building also is a separate theme. All the themes can be connected but need to be dealt with on their own first.