Hello!
To answer your first question, 'his prayers were adamant for my healing' means that his prayers were not helpful for my healing, or were not effective for his healing.
To your second question, 'victimizing the vulnerable is far beneath the people' means that criticizing, bullying, or torturing the people who are poor and who have nothing, or are already suffering are not good (beneath the people). Or is very inhumane and insensitive.
hope this is clear and helpful!