Is the divorce pronounced by the husband during a period of purity in which he had intercourse with his wife considered an irrevocable divorce? And are previous pronouncements of divorce, which the judge ruled invalid, to be counted as divorces? And is it permissible for the wife to remain with her husband in this situation?

If the matter is brought before a Sharia court, and the judge rules that the divorce did not occur, then there is no blame upon you for acting according to this ruling, even if others have issued a fatwa to you that it did occur. For the follower [of a madhhab] adheres to the judge's decree and disregards the mufti's opinion if the two conflict. And assuming the divorce did occur, your husband's taking you back with his words places you under his marital bond, and there is no issue in that.