I use the same navigation bar on my site for every page (as a SSI). It allows the nav bar to be updated on every page by updating one page. I have not had any problems using it - a lot of sites do the same.
To increase your
PR you need backlinks.
Google is not showing any links outside of your own site. (I know Google backlines are just sample!).
I would say get backlinks, increase content and then you may increase your
PR.
Alex