Long story short, I have no idea what I'm doing. And I was frustrated I couldn't see the (TrueNAS, formerly FreeNAS) iSCSI volumes from the ESXi host. Especially since I plan on backing up the the NAS and reconfiguring it as an honest-to-god fiber-connect SAN once I build-out my UNRAID NAS server. I reached out to a vSphere guy who explained what I was doing wrong, subsequently hobbling my way through an admittedly redneck solution. But it works:
iSCSI requires communication on its own VMKernel NIC.
Created vmk1 and assigned it the IP 10.0.0.5
Unsure if VMKernel NICs required discrete interfaces.
Attached a patch cable from a port in the ESXi QFE to a port in the TrueNAS QFE, and assigned TrueNAS interface 10.0.0.4
We need a vSwitch to handle traffic from the physical adapter to the VMKernel port.
Created vSwitch1 and attached both VMKernel and vmnic3
Let storage know what's going on.
Change IP to 10.0.0.4 for Static and Dynamic targets under STORAGE --> Adapters --> Software iSCSI
Once everything was saved and rescanned, everything just sprung to life!
The TrueNAS now shows up under Storage Devices, and VMguests have the functionality to map raw LUNS :)