You mentioned getting the "current" requirements. Do requirements change? If they do, does my son have to start over?

Yes, requirements do change from time to time. Periodically the BSA will update the Merit Badge books and revise the requirements. And no, your son does not have to start over. Once a Scout has started working on a merit badge, if a new edition of the book is published with different requirements, he should continue to use the same merit badge book he started with and fulfill the requirements in it to earn the badge.