I installed FreeBSD-12.0-RELEASE successfully, and everything is fine except that i can't start X because i get the following error: NVRM: failed to copy vbios to system memory NVRM: RmInitAdapter failed! (0x30:0xffffffff:747) nvidia0: NVRM: rm_init_adapter() failed! Then the kernel panic...
Because you have to install FreeBSD in BIOS mode, don't install it in UEFI mode.
Also the WiFi works but you need to add BWN_DEBUG and BWN_GPL_PHY to your kernel config, and compile and install the kernel.