You also helped me a GREAT deal. I spent a couple days struggling to get my system to boot. The system had the same "black screen" issue you described. Even weirder, sometimes I made it to the login screen only for the system to freeze after a few moments. Your tip about the iMac 16,1 was the fix!
by using iMac16,1 SMBIOS to avoid Black Screen like I mentioned before
I was using iMac15,1 like you had mentioned and didn't realize that was what was causing my problems.
In addition the confusion - the logs regardless of the boot outcome (if it was black screen, or login screen->freeze->reboot) I'd always gave the same last few lines: