I tried downloading this on my mac, but it can't be loaded once unziped, and in the macOS it's just a document instead of a loadable MacOS file.

you say the solution allready yourshelf, you need to mark this game as executable and give the game the persmission to let it run on your device.

i think this video can help: https://www.youtube.com/watch?v=pOV9HY0-WDU

another solution maybe: https://www.youtube.com/watch?v=NOW5dyA_JgY

i dont have a mac and cant test it myshelf but i got some positive feedback after seting the permissions.