I agree with tedster, the work you have to do is quite huge and since google always changes the calculations I won't bother. However just to inform you:
- robots.txt, disallows access to some pages, but doesn't prevent juice to be passed from pages linking to these ones. So juice is wasted.
- nofollow: actually nofollow links are links that wastes value. Since you're not passing more value to the other pages, you're just losing juice due to the nofollow links
By the way you're only risking to affect negatively your rankings and saying to Google that you're trying to manipulate your rankings sculpting your PR, this may be dangerous, so focus more on the new panda updates more than on PR.