I’ve never tried to install Qubes on an external USB drive, so I’ll try to guess the best way to do it. You could boot without usbcore.authorized_default=0 and rd.qubes.hide_all_usb since both won’t work in your case. You could keep rd.qubes.dom0_usb=X in your kernel boot options to attach the controller with your USB drive to dom0, give sys-usb the other USB controller under “Devices” in the settings and use that one for everything USB related.