This is a big topic and you've written a lengthy series of questions.


1. Assign a style for each level in your list. This can be a heading style. It can be a body-text style. Re-read Shawna's article.
Here is my chapter on numbering. Numbering in Microsoft Word

Use the links in that chapter that go to John McGhie's material.


2. Styles cannot be contained in global templates absent macros that implement them. Easier to use is probably [Quick] Style Sets.
See A Global StyleSheet in Microsoft Word? which predates style sets but works in the latest versions of Word. You can limit the styles that show in the Style Gallery for your templates and limit editing to only using those styles. This takes some planning.



3. This is my article on Understanding Styles in Microsoft Word. It does not address restricting editing to certain styles. It should and I hope to get around to it this winter.


4. Look at Templates in Microsoft Word and File New Variations in the Versions of Word. You will want your document templates in the Workgroup Templates folder. You may want to change the keyboard shortcut of Ctrl+N to use the classic File New dialog.


5. It sounds like you are working on a major project here. Consider customizing the ribbon using XML editing. See Customize the Ribbon (It doesn't take rocket science).

You can have a custom ribbon that gives quick access to all of your templates, dynamically, so that when you add or remove templates, the menus change. Here is a picture of the one used in my office.


6. You can also use custom QAT entries in your templates. Modifying the QAT in Microsoft Word

7. I am a great believer is using Global Templates. I use more than 10 with discrete purposes. One contains the Ribbon modifications with associated macros and QAT modifications. Another contains other QAT modifications and some keyboard shortcuts. The one with my numbering styles can be found here: Outline Heading Styles Global Stylesheet

Bottom line, you will need a great user manual and user training. You can't do it all in Word.