You can't actually ship a game on the porting toolkit without breaching the license. It's intended by Apple to aid porting to use Mac's native APIs one component at a time, but the license forbids redistribution or commercial use. The community can hack away with it however they want because Apple isn't going to chase every individual person, but a business can't ship it unless they want a nice call with Apple's legal team.

Nope. Unless Game Porting Toolkit is free and open like Proton, there is little to no prospect of the macOS gaming landscape to improve.