Take Root uses the term “former abducted-children,” um, shouldn’t it be “formerly abducted children?”

Nope, not if you are using “abducted-children” as a compound noun versus using “abducted” as a verb or adjective. (Think former beauty queen, former president, former Olympic athlete, etc). We use “abducted-child” as a title/label very intentionally when referencing family abduction because so many people mistakenly insist that children taken by family members are not abducted.