Oh dude, I could have missed your post, why didn't you ask in the groovymame forum ?
Looks like a buggy UEFI I'm afraid, this happens on some HP mini PC too. Your best bet is to isble UEFI and boot the USB stick in LEGACY mode. If not, find a PC that can boot LEGACY, install GA from there, then swap the HDD to your CRT rig. I can help you to reconfigure what's necessary