I'm not a frequent user here, but I want to share my thoughts on this situation.
Any misconduct and conflict-of-interest that involves a breach in private data confidentiality is an unacceptably reckless abuse of power. Even though this particular incident had minor consequences, the potential for major consequences need to be focused on. As such, I think that the punishment should be based off the potential harm rather than the actual harm. If an engineer knowingly builds a bridge with faulty materials but no one is hurt, that engineer will be punished as if the bridge collapsed and causes injury. The same concept should be applied here.
I believe that your administrative powers should be stripped indefinitely. Your role is to make decisions in the best interests of the SMW community. Your selfishness and recklessness to sell personal info online violates this trust, and violates the sole reason for being an admin in the first place. It doesn't help that the tone of your apology attempts to downplay the magnitude of this; i.e., "even though no one was harmed."