Is it permissible to sell Netflix accounts that contain scenes of nudity, immorality, and fornication, knowing that the seller disavows the sins of the buyer, and this sale is his sole source of livelihood?

As long as the website contains objectionable content, it is not permissible to work in selling its accounts. Your statement to the buyer that you are absolved of his sin does not exempt you. Similarly, it is not permissible for you to view that objectionable content, and your claim of not being affected by it does not make it permissible for you to view it. Therefore, repent to Allah and leave this work unless there is an absolute necessity.