What should someone do who swore not to masturbate, and made it binding upon himself to pay 5,000 pounds if he did, then he did it six times, and he is unable to pay the full amount? And is he required to pay 30,000 pounds, or 5,000 pounds, or feed ten poor people?

If someone takes a single oath concerning multiple things and then breaks it, only one expiation is required, and the oath is dissolved by the first breach. What is obligatory for you is an expiation for an oath, which is: feeding ten poor persons, or clothing them, or freeing a slave. If you are unable to do so, then fasting three consecutive days. And you must repent to Allah.