How can one overcome feelings of hatred towards parents—especially the father and mother—resulting from their mistreatment, and avoid incurring Allah's wrath or entering Hellfire because of these feelings, knowing that there are psychological and health pressures that have led to thoughts of death?

You must be patient with your parents' wrong actions and not show displeasure towards them, not even by sighing. Be gentle when requesting the obligatory financial support from a negligent father, and be diligent in remembering Allah and supplicating for their rectification. Keep company with righteous sisters. As for the fiancé, he should be encouraged to marry, and it is not permissible to break off the engagement due to family problems. It is also forbidden to wish for death or to contemplate suicide.