The gold market cap has always been the approximate amount of gold that has been extracted. While I don’t think anyone can give you an actual precise number, the approximate number is pretty widely known and tracked as we extract more.

Quite possible. I’m not an expert and working from memory, so I could very well get something wrong

Yes, actually. They’re both different mixes of plutonium isotopes. Iirc reactor grade plutonium is far more stable than weapons grade (because blowing up is less desirable for reactors than bombs), and has some different properties when used.

same. Ive played it for about ~10 hours on the steam deck so far, and i have my FPS counter turned on at all times; never seen it dip below 40, and i dont think ive touched any settings. On an original steam deck, not an OLED, though