Regarding records: Thanks for looking for baptisms. Don't restrict the search to baptisms for children of Dirck and Sara. His profile says "Dirck and Sara appear as sponsors for numerous baptisms in Rochester as late as 1778" -- see where they appear together as witnesses. They may have witnessed baptisms for her siblings' children.
Regarding age: Although "j. d." stands for jonge dochter and it is often literally translated as "young daughter" the Dutch term is better understood as "maiden," meaning that she was not previously married. (I've also seen it rendered as "spinster.")
Sara/Zara born 1730 was a bit old to be marrying for the first time in 1758, but not every woman married young, and it makes sense that a 38-year-old widower would not marry an 18-year-old as his second wife. Several of my New-Netherland-Descendant ancestors, both female and male, were relatively old at their first marriages. I suspect that some of them had been unable to marry earlier, because of being the "child on duty" who was expected to run their aging parent's household or farm.