Under the Equal Pay Act of 1963, the scenario that is illegal is paying a woman less than a man when both perform the same job. The Equal Pay Act mandates that men and women be given equal pay for equal work, meaning that if two employees are in the same position and perform the same job, they should receive the same compensation regardless of gender.
The other scenarios, while they may raise issues of discrimination or workplace fairness, do not directly violate the Equal Pay Act.