Note that "Jewishness" has the meanings both of "adherence to the religion of Judaism" and "membership in the ethnic group 'Jews'". People of both groups are listed here.
... second line is a compound
of "mat" (me) and "stha" (standing, staying at) and
means "they are in me".
"-aham" (I) in the second line is nominative. na caaham = ...