How can one atone for financial and moral sins related to the rights of others after repentance, especially given insufficient financial means to redress financial injustices, and how can one deal with backbiting without spoiling relationships?

Allah accepts the repentance of a servant, no matter how great their sin, as long as they have not reached the gurgle of death (i.e., the death rattle) or the sun has not risen from the West. And He, the Most Glorified, has promised the repentant forgiveness and mercy. Sincere repentance (Tawbah Nasuh) involves abandoning the sin out of fear of Allah, regretting having committed it, and resolving never to return to it, while also restoring injustices and rights to their rightful owners. Repentance from backbiting involves discrediting oneself before those in whose presence one backbit, and seeking forgiveness from the wronged party if possible, without causing further discord. If you fear discord, then turn to Allah and mention the one you backbit about in a good light. Repentance from theft involves returning the stolen goods to their owners; if you are unable to do so, it remains a debt upon you. Your seeking forgiveness from those you have wronged and following bad deeds with good deeds may lead Allah to bear on your behalf what you were unable to fulfill.