Is breaking off the engagement with the current fiancé considered an act of disobedience to one's deceased father, and a cause for his anger after his death, considering that the marriage was intended to please him during his severe illness, and due to painful past marriage experiences?

Parents do not have the right to compel their child to marry someone they do not desire. If the child refuses, they are not considered disobedient. You are not obligated to obey your father regarding marriages you do not desire, especially if you fear harm or discord. If the marriage contract has already been concluded, your mere lack of desire for the husband is not a valid reason to annul the marriage, unless there are legitimate defects that permit annulment. If you dislike your husband and fear neglecting his rights, you may request khulʿ (dissolution of marriage initiated by the wife). We advise you to be patient, seek counsel, and perform Istikhara (prayer for guidance). If the young man possesses religious commitment and good character, Allah may bless this marriage.