Is the $100 that the questioner took from the travel agency owner considered a debt that he must repay, given the circumstances surrounding the temporary work agreement and the claims of fraud and non-receipt of the agreed-upon wage?

It is difficult to rule on these disputes based on the statement of one party alone. If the office owner secured the agreed-upon work, then you must hand over his full commission and pay off your outstanding debt, because the contract becomes binding upon completion of the work. However, if the work was not completed in full but you benefited from what he did, then he is entitled to a fair wage for his work, estimated by experts.