Is it considered disobedience to the mother if the son chooses a literary specialization despite her forcing him into a scientific one? And is he sinful if he deliberately fails the high school exam to avoid studying medicine?

We advise you to strive diligently in your current studies, while relying on Allah and having sincere intentions, and considering it an act of obedience to your mother. Specializing in medicine is of great benefit. Al-Shafi'i said about it: "I do not know of any knowledge after the halal and haram more noble than medicine, except that the People of the Book have surpassed us in it." Be gladdened by the blessing of your obedience to your mother, and know that your medical specialization does not prevent you from studying Islamic sciences or other fields. If you do not find yourself suited for medicine, there is no harm in switching to a specialization that suits you, while continuing to be dutiful to your mother. We also advise you to make abundant supplications.