What is the average runtime value? Glancing down the column, it looks like a little below 2 days, which is exactly what I would expect from a dual core.

Yes, one day it only reported 17 hours - but the next it got 3 days and 11 hours - you have to average it out.

The low result count is presumably due to the large work units.

If you are still worried that BOINC is cutting out, then try and find a processor graphing utility. Sorry, I don't know what to recommend for Linux - perhaps someone else has a recommendation?