I doubt I can help you out, since I seem to be in the same situation as you, but there are a few other things I tried that might work for you even though they didn't seem to help me.

You said you followed the "Comprehensive flashing guide". Did all the steps appear successful then no vibrate and no boot, or was there an error reported in one of the steps? If your battery was totally dead, flasher should charge it before continuing.

BTW, with the phone off (after holding power button for > 8 sec.) will it appear to charge when plugged into USB port or charger? I.e., does the LED breathe (slowly turning on and off) for a while then remain on steady?

Have you tried the "Fixing MALF state" instructions? I followed them and was able to mount the N9's volumes. I did find a /var/malf file on my unit indicating too many software reboots. If you find this file on yours, you might check to see what error is reported.

Also, while you have your phone volumes mounted, you can recover some of your data/photos if you haven't already backed those up. Even if you've already done the EMMC flash, you can probably still recover the deleted photos and videos with "photorec" on Linux. Probably something similar for Windows, but I don't know. If you've already used the secure delete, this won't work.

Wishing you better luck than me.