OK, let's start with the basics. Read this:
Barry's Tire Tech
and this:
Barry's Tire Tech
What you should get out is that there is a compromise involving Treadwear, Rolling Resistance, and Tracuion. You'll want to choose a tire that gives you the compromise you can be comfortable with.
Second is that larger tires give better RR - all other things being equal. That should open up a few more options for you - but sadly your speedo will be off.