It appears to me that the vertical bars are just a division of the * / * / or * / * symbols showing what is iambic pentameter and what is iambic tetrameter. And wow...what a challenging assignment!
I think you have to do whatever you think would make this the most understandable. Just insert well-worded transcriber's notes explaining your format. Putting spaces in where the vertical bars appear seems to me to be a good idea. To my knowledge, there are no guidelines in other documents. I assume you've scoured the rules on IPA...that would be my first suggestion.