Is it considered disobedience (ʿuqūq) to marry a girl whom the father rejects because her father insulted him, knowing that the father refuses reconciliation with the girl's father?

If your not marrying the woman will result in harm, or if your father is preventing you merely due to a disagreement between him and her father, then you are not considered disobedient by disobeying him. Nevertheless, we advise you to strive to please your father and to reconcile him with the girl’s father, even if it requires the mediation of wise people. If that does not succeed, then look for someone else, unless leaving her would cause you harm.