Daddy O means Dad, just a hip/cool word that was popular back in the 'groovy 70's '. He used the word because it rhymed with 'radio' in the next line.
AM Rock, popular music played on AM radio stations usually short 3 minutes songs before FM radio came along and changed the landscape.
Sock Hop is simple a school dance with a band or Disc Jockey, at least that's what we called them when I was in school.
MC is a master of ceremonies, I refuse to associate this with 'rappers' which is the urban dictionary definition, MC's were around for decades before rap came along.
Feeling all of 45 going 15, just means he's feeling young and carefree again, not necessarily childish.
What's wrong with children listening to music on the radio? I know I grew up listening to grown-up's music playing all the time.