Don't give up! Your BIOS doesn't have any options for changing between discrete and integrated cards? What's the order your modules are being loaded? Are you using Nvidia's prorietary blob or nouveau?
I managed to make my ThinkPad P51 (Intel HD 630 and nVidia Quadro M1200) work by using Arch's bumblebee tutorial: https://wiki.archlinux.org/index.php/Bumblebee#Output_wired_to_the_NVIDIA_chip