what programs did you use for tweaking? did you reset these programs back to defaults BEFORE uninstalling them?
The turning black- that was your graphics driver crashing HARD- thankfully it recovered most of the time.
from the sounds of things, you might have permanently damaged your graphics card. If the sensor is damaged as well, it's possible it is reading temperatures that are higher then their actual temperature.
It's possible, but probably not a good idea- especially with OEM cases where fans are placed in specific configurations to optimize cooling.
Firmware, (or more precisely, the Video BIOS) as far as I'm concerned, should NEVER be flashed, except in special circumstances- your card appears to be a write-off at this point, but a video BIOS flash should only be performed as a last ditch effort.
since your obviously having a little heat problem (the CPU is 59, which isn't terrible, but lower is always better).
have you cleaned out any dust on heatsinks?