Looks like you've determined that the video card is dead.🙁
Does any of your capacitor on the motherboard appeared abmormal?
I know you said you've cleared the CMOS. Can you try to dismantle the entire system? Disconnect all cards and connectors and remove the CMOS battery.
While the board is out of the case, repopulate the board with the cpu, heatsink, memory and video card. Connect the ATX power supply and try to turn it on. You'll need to short the power pins on the motherboard header with a jumper.
If it boots up, power it down and put back the battery.
Goodluck.