You have already discovered that there are problems with using Bookmarks for this purpose.
1. Bookmark names are case insensitive
2. Bookmark names are more limited than text on the page (eg can't include spaces, start with a digit, include ()@ or other characters, must be less than ~40 characters etc)
3. Bookmark names are not automatically updated when text on the page changes
4. Bookmark ranges could be 'broken' easily (and invisibly to the user) by edits to text in the document.
5. Bookmark names can only appear once in a document

If your intention is to see a list of the document content so people can quickly navigate to locations in the document then there are two features that most users are already familiar with for exactly this purpose:
a) Table of Contents
b) Navigation Pane

IMO, both of these features avoid all the limitations of bookmarks. I can't see any benefits of using Bookmarks for navigation other than cross-references. But if you are using bookmarks for cross-refs then you can name the bookmark completely independently to the actual text it is pointing at.

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Andrew Lockton
Chrysalis Design, Melbourne Australia