I don't think so... at least not based on the "Horror Movie" song. The Skyhooks were a popular Australian band in the 70's. My aunt sent me one of their albums when I was a teenager... in fact, it had this song on it.
They are hardly what I would call a demonic heavy metal band. They had a TV show in Austrailia and are more of a glam-rock type band. Kind of a cross between Adam Ant and the Monkees.
I would suspect EOM has some connection to Australia or possibly Britain, and is much older than Gadahn. The Skyhooks were almost unknown except in those countries and became ancient history long before he was born.
Heavy metal and death metal bands have done several covers of the Skyhooks' "Horror Movie". It's all about the lyrics for EOM/Gadahn, not the band. I never said he was a Skyhooks fan.
I'm thinking you're right. The more info I look for the less I find. I kinda think he's just a fantasizing wacko.