Tony, you additionally need to know, that dokuwiki requires some restrictions for pagenames and namespaces: As far as I remember: lower case, no spaces, etc.
For pages you can use "useheading", what you already did. For namespaces there is no such possibility; you need to make use of the workaround turnermm advised.
I am not sure if I understood you correctly/sufficiently
In our wiki we have the navigation in the SIDEBAR, which always remains visible, but takes space: There is just one page "navigation" or "sidebar" or however you call it with (as only content) the indexmenu-call/order. This file is made known as the sidebar-content via the dokuwiki configuration.
Perhaps there is a misunderstanding: As far as I understand you "cannot" upload a "file to a page". You upload any document into the media-folder, which well can have a similar structure concerning namespaces as the data-folder. On the page you only insert a link to where dokuwiki should find the file.
Scott, currently I am testing a combination of doodle-plugin, with which you can do a job-page in each (project-)namespace. With the include-plugin I collect all these job-page to get a general overview about all jobs/tasks, which need to be done.