I'd prefer something a little sturdier. I might occasionally wear this as part of a costume, and I'd hate to lose the whole ear & emitter assembly because of some glue.
i would say negative on the jb weld threads holding for long. as far as the rabbit ear pin goes, there's no rule says you can't use a long machine screw.
why not drill and tap a piece of key stock for the clamp bar? Or grind down the opposite edges of a nut?