This is a decent summary of fatigue wrt volume vs intensity:
http://www.jtsstrength.com/articles/...gue-explained/
It is a little different than your situation because the point of the article is to discuss fatigue in the context of "the inhibition of maximal performance that comes about as a result of stressors imposed on the athlete." You're not really worried about being able to squat your max on any given day.
I see pros and cons to ditching 3x5 in favor of a couple of moderately heavy singles right now:
Pros:
-progress towards your prior max (whatever it was) should be faster
-I would think the reduced volume would leave you with more energy for running and other activities
-greater degree of daily flexibility, allowing you to better tailor your daily workouts to how you're feeling that day
Cons:
-fewer overall reps means less grooving of technique
-less hypertrophy