Are fictitious marriages and divorces religiously null and void, entailing the unlawfulness of the money earned thereby? And what is the legitimate course of action in such a case?

Fictitious divorce and marriage are not permissible, as they constitute trifling with and belittling the Shari'ah of Allah, due to His Almighty saying: "And do not take the verses of Allah in mockery." As for money acquired from a lawful profession due to this deception, there is no harm in it, but one must repent to Allah Almighty.