Flash it back to full US v6.20 fw saved as 097201000620.rgn, or if that won't flash, as OUT.rgn.

Did you do HWID overide to 0972 in RGN_Tool when you flashed to modded fw? As far as i know US/EU 14xx doesn't support ecoroute HD.

If you get it safely back to full US/EU, you could try again using an earlier version of SG/MY combined with US/EU boot.bin. That may be safer that trying to flash directly from higher to lower SG/MY.