As of today I have tried disabling CSM, and also tweaking all CSM settings to attempt to install FreeNAS with no success... I either get a reboot each time, or I get a blank screen and eventually a reboot.
In addition I've pulled all my expansion cards, pulled all drives from SATA, I've disabled SATA in BIOS, I've disabled LAN in BIOS, I've tried changing USB settings, I've used default motherboard settings, I've cleared CMOS... I've contacted ASUS for the very latest update (November of 2016), and still issues with installing FreeNAS on this motherboard. I've tried both the latest stable build and corral in all scenarios.
When I don't have a blank screen here is where it reboots:
https://youtu.be/tbilIKWc_yY