#1
Good dvd for pratique rhythm guitar acoustic or metal/rock!!!

Or good youtube lessons
#2
Rhythm Guitar by Musicians Institute is a good primer for rhythm guitar... beyond that, once you know the basics the best way to learn rhythm is learn a hell of a lot songs and relate them to the correct theory and fretboard knowledge. Hope that helps
#3
Yeah learn songs... But dont only learn them, take those chords and make your own rhythms from them, throw some chords out, transpose some stuff and create your own songs. Find out what kinda of chord progressions you like best, why chords are used in the places they are used etc.