I think that duplication of data will complicate things quite a bit. I would probably use a field user field on the CPT to relate each post to a user. This field could allow null so that if there is not user that matches to post it would just be empty. Then I’d store all my custom data on the CPT.
Then you can create a front end form with acf_form() http://www.advancedcustomfields.com/resources/acf_form/ and allow them to edit what you want them to edit by specifying the fields to show in the form.
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