They dont go into here.. but I thought that NASA also used like 250nm chips in space for radiation resistance. Are there even any radiation resistance GPUs out there?

Absolutely not, although the latest fabs with rad-tolerant processors are at ~20 nm. There are FDSOI processes in that generation that I assume can be made radiation-tolerant.

NOPE, RAD hardened space parts basically froze on mid 2000s tech: https://www.baesystems.com/en-us/product/radiation-hardened-...

It seems not; anti-interference primarily relies on using older manufacturing processes, including for military equipment, and then applying an anti-interference casing or hardware redundancy correction similar to ECC.