Correct punctuation citing names as given in church records.

Hello,

I am working with many birth records found in various German Kirchenbücher.  Often, the records I find are listed by only the child's first and middle (baptismal and given) names. The surname must be derived from the  information given about the parents. 

For example, I am working on an individual known to me as Johann Paul Dieterle.  Since his birth record lists him only as Johann Paul (and provides the surname of his father later in the record), would it be appropriate for me to "add" his surname using square brackets?

"...birth record for Johann Paul [Dieterle]..."

I've also found that there can be multiple ways to spell the father's surname.  This specific record lists the father's surname as "Diederle".  Should I use quotes within the brackets to indicate exactly what the record provided?

"...birth record for Johann Paul ["Diederle"]..." or

"...birth record for Johann Paul ["Diederle" vs. Dieterle]..." to show this is not the typical spelling.

I want to give the clearest reflection of how the Kirchenbuch presents the information.  Thank you in advance for your suggestions.