Is the divorce considered irrevocable, given that the husband's intention was a revocable divorce, and considering that the officiant wrote it as a "divorce in return for release" (khul'), and is it permissible for the husband to take his wife back after what has happened?

Khul' is the separation of a husband from his wife in exchange for compensation, and it is permissible by the Qur'an, Sunnah, and scholarly consensus. The husband's intention is not a condition for its validity.

If khul' occurs under duress, it is not valid. Duress is anything linguistically defined as compulsion and perceptually recognized, such as threats of killing, beating, imprisonment, or destruction of property, or threats against another Muslim involving killing, beating, imprisonment, or destruction of property. Insults, verbal abuse, and taking a small amount of money do not constitute duress.

If there was no real duress, then the khul' is valid, and the wife is irrevocably separated from her husband. It is not permissible for the husband to take her back except with a new contract and her consent. Ignorance does not negate the sin for the disobedient, but it is generally considered an excuse that removes accountability.

If the woman's guardian refuses to return her to her former husband's marital bond despite her desire to do so, this is not permissible for him, and she has the right to take her case to the Sharia courts.