If someone swore not to return to a sin, then returned to it and offered expiation, sought forgiveness, and repented, then swore a second time that if he were to return to it, he would feed a thousand needy persons, would two expiations be binding upon him if he were to break his last oath?

If your friend swore a single oath not to return to the sin, and to donate a thousand meals if he does return, then he owes one expiation if he breaks it. However, if he swore a separate oath for each matter, then he owes an expiation for each oath. He is not obligated to donate the meals after the expiation for the second oath, but if he does donate them, then no expiation is due from him.