With apologies in advance: could you go with Via Stulta or Via Stulti? Via Stulta is the "Foolish Way," analogous to Via Negativa in that stulta and negativa are adjectives agreeing with via. Via Stulti is the "Fool's Way," using a possessive form of the adjective functioning as a noun (as we do in English in expressions like "The home of the free").

The moral of the story is never to use DuoLingo for Latin, apparently.