Hi
I am going to be more positive. :-)
I would enable the AMD GPU, and remove the nVidia one to see if you can get the OS installed.
or
If you can get the installation to drop you to a command prompt, download some nVidia drivers for FreeBSD and do what the documentation tells you to install them. manually start xorg, look in the log files to see what xorg is trying to do, and where it is failing if this doesn't work.
Do reply if you get your installation to work.