You are awesome, yes this worked. I guess I should not rely on unifail anymore. Thanks again!
EDIT- I think I spoke too soon. It booted the installer fine, it installed fine, it even booted into Mohave fine, but I went and restarted without fixing the internal EFI, and now it won't boot via the USB installer's clover, doesn't matter if I try to boot to the internal HDD or the usb's installer. I keep getting "Waiting on..." and something about IOProviderClass string ID="1", I suspect it's something to do with USB, but why would it have worked then all of a sudden stopped working. Same USB drive, tried all three USB ports on the computer...