1. You can only have two kinds of music for bosses: music 0 or music 1. You could change the music by removing the orignial boss music files in your JJ2 directory and replacing it with something else, but other ppl would have to do the same if they want to hear the custom music. I'm not sure what 'delte' means but I guess that you want to remove the music. Well, you can only do that by manually deleting the boss music file from your JJ2 directory (boss1.j2b and boss2.j2b.

2. Nope, I'm a tileset noob as well.