Success! I jacked the oven up to 350 and went for broke. My wife yelled "I smell something" so I figured it was hot enough. Gave it a twist as instructed and it popped apart. One outer leg had already fallen off, so I am thinking that the core was already cracked by the earlier attempt. No harm, no foul, super glue to the rescue.
I APPRECIATE all the advice that was given. A special thanks to Chuck Harris for his concise instructions. Now to figure out how to make and wind a new bobbin.