It's fully possible your GPU is broken. If what you say about temperatures is correct, it's not the fans or the pads. Overheating GPU will usually just throttle until it's cooler again.
If you tried reseating and it's not a dust issue, nor did you reseat it incorrectly again and it's not a driver issue, you should try to find out if your GPU is the component at fault here. Try removing your GPU and run a benchmark on the iGPU if available, otherwise you might need a different GPU for testing. If that all goes fine, you know your GPU is at fault.
Other things that can be broken:
- the PSU
- The PSU connector cable
- the motherboard
- RAM (disable XMP?)
- BIOS settings (power saving, resizable BAR)
- and of course your storage for which you can try CrystalDisk or similar to detect errors.
Assuming you're on Windows you can also check the Event Viewer logs to find out why stuff crashes.