I don't think it is "very wrong" - I think it's pretty common for a smallish site with good internal navigation. It's natural and not a problem for Google.
I would not even start trying to sculpt PR. First, Google has changed the way nofollow works, so that approach is futile. Second, if you don't allow crawling for a lot of pages (robots.txt), you're likely to break all kinds of important circulation for your link juice. Remember that PR calculations iterate over and over, they do not stop after just one "hop".
Most people who have tried to "sculpt PR" have ended up hurting their rankings. For the very few who've had small success (and the potential gain is small) they find that it isn't worth the intense investment of resources. This is partially because Google has many times changed the way PR is calculated compared to the initial patent - and we don't even know the details any more.
for 90 % of them I don't want to rank as the keywords are not request.
If the keywords are not requested, then it doesn't matter if they "rank" or not. Google watches search impressions for the page. If there are no searches, then there are no impressions.
I'd say you should relax about all this. Make sure your pages are useful for your visitors and the internal navigation is logical and easy to use.