Does a divorce issued by the husband four separate times during extreme anger take effect, given that he does not remember what he said, does not desire divorce, suffers from severe nervousness, abuses hashish, and has cancer, noting that he threatens his wife with death during fits of rage?

If your husband's anger reaches the point of losing awareness and discernment, then the divorce does not take effect. However, if it does not reach this point, and it is normal anger resulting from discord and disagreement, then the divorce does take effect. You should advise him to repent from consuming hashish and turn to Allah.