Is the supplication "O Allah, do not let me die while I owe rights to Your servants" valid and acceptable?

There is no harm in supplicating with the words, "O Allah, O Fulfiller of Needs, O Answerer of Prayers, O Forgiver of Sins," as long as it does not involve sin or severing kinship ties. It is permissible for the worshipper to supplicate for all their worldly and otherworldly needs, even for small matters.