This is good news. That's recovery.
I know you're having a hell of a time here but don't worry, you can come out of this for sure.
Now the auto root zip you got from the XDA thread, I want you to copy the PC36IMG.zip RUU file that you have and put it in the folder the zip from XDA was extracted to.
Now with your phone on the red triangle screen, open a command prompt in to the folder and type this:
This will take some time to copy over but that's OK, when it's done type:
When the phone comes back up in the white menu, it'll either scan the sdcard and ask if you want to apply the update, hit volume up for yes, if it's just a menu, select "bootloader" with the power button.
When the update is done, select Yes to reboot, your phone will now be stock 3.7