That is NOT how this worked 10 other times and it is not working now
When the usb is just a mounted .iso from Boot up it reads it like an install disc. Like if you had a DVD with abunch of folders on it, it couldn’t boot. If it was an .iso it would
I would recommend that you document the things that you thing worked. As everyone else had mentioned, your should have had a USB drive with folders and stuff not an ISO. You machine SHOULD have booted from this. That is what I meant by a SANE machine.
Since that is not the norm for your system and you worked on this for over 6 days at least, anyone else who has your kit should benefit from your trials and tribulations. I don’t envy you but you have awesome persistence!