I can't really test this with my phone without going S-ON and upgrading HBOOT myself. And since you're already at this point, uh, I'm not going to go there, lol sorry. But, if you find that you cannot brick your phone and it was just a fluke. Try putting a file on your sdcard titled SMART_IO.crd doesn't matter what the file is, could just be a blank txt file you've renamed. Boot the phone to bootloader, insert an sdcard with this file, then switch to fastboot mode, then back to hboot mode. Phone should lock up, maybe this will trick it into the emmc mode. I never did this while connected to linux.
Now that we know the mode exist, it's just a matter of finding a solid way in. Everything else about this method is solid. It may even be possible to brick it by messing with the radio and still get into the emmc recovery. That would require repairing the radio partition too, and be a lot riskier though. Also did you verify that the phone doesn't repair itself after a battery pull. It could just be the timing of something that you did without even thinking of it.
If you need to, maybe lock this thread down to keep the haters STFU and get together with Crackanug, video tape everything you do, and see if he can/will try to emulate it.
Whatever happens, this is a hell of a lot closer than any of us have been on the 3VO. You had 1.40 and went back to 1.50 purgatory. Not many would do that to themselves. Mad props dude.