I also knee-jerked that the dash should be inside the quotation mark, however, in the example shown here wherein there is an interjection, the em dash outside is correct. (When the em dash ends the thought though? INSIDE!)

Though, I agree; I don't think there should be a comma after the ellipsis. I'll look into that and have the article updated if necessary.

We have an article all about Speech that Trails Off that might interest you.