Is it incumbent upon the wife to observe 'iddah after the husband curses the religion or the Lord, and when does this 'iddah end, especially if the one who cursed has not consummated the marriage with his wife and has repented of his action?

Cursing the religion is major disbelief. Whoever curses the religion has exited Islam, and ignorance is not an excuse for it because it is known by necessity to be part of the religion. Uttering the two testimonies of faith after apostasy is sufficient to return to Islam, and one must be cautious in the future. If you have not consummated the marriage with your wife and there was no lawful seclusion, then the marriage is annulled by apostasy, and she is not permissible for you except with a new contract. If there was seclusion, the waiting period (iddah) becomes obligatory according to the majority of scholars. The marriage is annulled according to most scholars, and according to some, it remains valid if you return to Islam before the expiry of the iddah. The wife's iddah is three menstrual cycles, or three months if she does not menstruate, or by giving birth if she is pregnant. If you return to Islam before the expiry of your wife's iddah, then your wife remains under your marital bond, and you do not need a new contract. If your repentance occurs after the expiry of her iddah, then she is not permissible for you except with a new contract. Apostasy is an annulment (faskh) and not a divorce (talaq) according to most scholars.