What is incumbent upon me, and should I complete my fast, after I intended to fast at night to make up for a missed day, then I doubted at dawn that I had revoked the intention, and water entered my stomach during ablution by 99%, then I remembered that I had not revoked the intention?

Your fast is valid as long as you did not intentionally drink water. The original ruling when in doubt is that it did not enter the throat. And even if it did enter due to forgetfulness or an overwhelming circumstance, and not intentionally, your fast is valid and you are not required to repeat it.