"Adamant" means unshakeable or unwavering, so he prayed determinedly for the narrator's healing. If something is beneath you, you're too good for it. The people of the Downtown Eastside are too good or honorable to participate in victimizing vulnerable people, people who are already poor or weak or disadvantaged.

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!