Did 2 whole miles!!
Somewhat emboldened by the one mile run yesterday and day before, tried to stretch myself and did a two mile run today. Still kept the run slow. Was able to finish out without the calf muscle pain coming back.
I have to isolate the cause for the original injury – whether it was the quick buildup of miles in September or the new shoe I was trying. (For now, I am using an old pair of shoes).