Does the aforementioned divorce count as a single, revocable divorce or as an irrevocable divorce, given that it occurred during menstruation?

If you were aware of what you said at the time of divorce, then an explicit, effective divorce has occurred from a responsible, volitional husband. Its occurrence is not prevented by the wife being in her menstrual period, nor by her doing so as a trick to test your love. Your repeating the phrase three times does not result in three divorces occurring; rather, one divorce occurs, as long as you did not intend to effect three divorces by repeating it. And as long as you have not divorced her before that, you may take her back during her waiting period (iddah (definition)).