Sleeping also used to keep your health up during a fever even if you were not well fed, but not anymore. I'm not sure if that's a bug or an intended change of mechanics.
I'm pretty sure that "slow healer" is only supposed to affect wounds that show up on the health panel (bleeding, scratches, broken bones...), not things that only show up as moodles. "Prone to illness" should increase your rate of zombification (though I'm not sure whether it should affect the fever triggered by "hypochondriac") and increase the chances of getting ill from bad weather.