How get index to work correctly?

At the top of the page, there is no option for "view" so that I can go to master pages.

The file is locked!

As for the indexing, perhaps the file you are linking to is locked? Follow a link and check out the menu bar. An unlocked file looks like this:

A locked file looks like this (note the very different menus):

If the file is locked, click the golden padlock icon 7 icons from the left of both toolbars.

If the file is unlocked, then it's just a misunderstanding on how to edit an index marker.

• Special > Marker will open the Marker panel. Keep it open while editing!
• Follow a hyperlink (Control Alt click a page number) and then don't do anything except direct your eyes to the Marker panel. Somewhere on the page a marker is selected but if you click you will deselect it.
  
• Just click inside the Marker panel and edit the marker, or delete it.
• Save the file, update the book to see the change reflected on the index.

The number size is a feature, not a bug. You can change the look of the numbers independently from the text entry, and you might do so because the links are on individual numbers and you want to highlight them for the reader. You may not have noticed yet, but the separators will also be the wrong size. Change the para tags for both on the IX reference page:

For example:

changes the page numbers from:

to

Remember that reference page changes don't take effect until you update your book.

Try deleting the .lck file. I once had a file I couldn't edit and iirc this solved it. To reset the font size I have to Select the whole index, except the first heading, and click default font, then select the first header and use update all in the paragraph designer. Maybe there is a better way.