In all fairness, you may be right. Maybe Calvin never said there was a "span long of babies in hell" but, then, what he says in your quotes makes no sense if God predestined some people to hell and some to heaven.
It seems Calvin is toying with the idea, to wit: "I everywhere teach that no one can be justly condemned and perish except on account of actual sin," that somehow hell is a destination only for those who actually commit sin—a works-based cause and effect!
We all commit sins. Calvin and Scripture remind us that those who end up in heaven have had their sins paid for by Christ by the grace of God.
Men cannot earn their salvation. Infants cannot earn their salvation.
All of grace.