"The New England Historical and Genealogical Register" (NEHGR) mentions this same James Alexander twice:
Volume 6 page 87 Volume 24 page 289
These make interesting reading - and would be especially so if someone knew that their ALEXANDER line could be traced to this family. There is no 'genealogy' that would tell us that James went on to have heirs, but it does describe the captives taken from various places and held at Quebec. Later (in October 1695) Matthew Cary paid ransom for some of the captives and James Alexander of Casco was one of those returned. So he did evidently survive his captivity.
Also from Casco were Mary Swarton, Jesp'r Swarton, boy, Samuel York and Thos Baker, boy.