I heard that if you hold the sync button then power up it clears a bad update! "you could try that".
have you done the screw fix through the case and/or motherboard?
Have you tried extra cooling mods for other board chips?
Im no expert but im sticking in my corner and saying that the 2 spacers between the board and sink are slightly 2 thick!
I did leave my box switched on deny cooling to gpu till 2 red lights power off then cool down.
best of luck with your rrod fix