What processor and what hypervisor were you trying to pass through the iGPU?I used to run it in a VM running on a XEON. I tried loads of times to pass through the Intel graphics through (this Xeon version has it) and it doesn't work. I ended up essentially building a similar machine and running Windows natively. I like the Xeons as they have ECC memory and I use a RAID to ensure the system is stable. Everything gets backed up onto a ZFS NAS.
How many cameras do you have on that machine to get that kind of usage on the VM (now many megapixels).