What is the story of the statue, with just the legs and half the torso, which can be seen when traveling south on Route 58, Monponsett Street?
It is half of a statue of Myles Standish. See the Halifax Reporter for details. In 2017, the legs were moved to a location near Dwight Street and Ocean Avenue as the property that they had been placed upon was sold.
Was Kilroy, of "Kilory Was Here" fame, a resident of Halifax?
Yes, James J. Kilroy was a resident of Halifax while he was a welding inspector at the Bethlehem Steel shipyard in Quincy, Massachusetts during World War II.