Clear indication Hesher is a projection

The pool scene.

We see a transformation to Luke Skywalker. It was like, one minute he was there, and then he wasn't. That sealed the deal for me.

It's pretty obvious that everything going on is in the Star Wars universe. Perhaps this was Luke's possible future if he hadn't turn his dad over to the light side? Or maybe Luke died altogether and this was his hell? Forced to enjoy metal music and get high? It would also make sense he always wanted to blow *beep* up since if he died in Episode 6, the Death star would never be destroyed. It would be only logical he would lash out like this as "Hesher".

I enjoy when I understand movies like this. I'm so deep, man.