one of the twelve. So in all three Gospels. Had probably become almost an appellative by the time the Gospels were written (as "he that betrayed Him "had).
multitude = crowd.
staves = clubs. As in Mat_26:55 and Mar_14:43, Mar_14:48. Luk_22:52. Not "staves", which is plural of rabdos = a staff for walking, as in Mat_10:10. Mar_6:8. Luk_9:3 and Heb_11:21.