Those are all really good questions, I don't really know the answer to. Not all coins have the wild spikes like bitcoin. Monero has been fairly stable. I haven't listened a game before, but I'm pretty sure you can pick which currency you want to get paid in. The conversion rates would be roughly the same for crypto.
However, Valve is no stronger to imaginary digital assets that wildly fluxuate in real world value. If there was any company that could figure out how to process crypto I think it would be them.
I scored 18/21 on https://e-mail.wtf/ and all I got was this lousy text to share on social media.