An hour later and I managed to find a way to open it, although I'm not sure if it's the safest so take this with a fat grain of salt. I opened the terminal, and typed in chmod +x once I typed that I went to the game file pressed show content for the file Mac Fix -> content -> MacOS drag the file you see into the terminal right next to where chmod +X is entered. at this point, the file you had dragged in should've turned into a black square with exec on it. it should open and you should be able to play it! Again I really just fiddled around with the files so I'm not so sure if it might ruin anything. and if it says cannot open due to unidentified, open system preferences -> security -> click the lock to make changes try to open the game and re-check system preferences, and you should see a button to just ignore the unidentified. this part doesn't do anything to mess your mac up.
I'm glad you managed to figure out a way that worked :3 I don't have a mac myself, so when people tell me all the different ways they've managed to successfully open stuff, it doesn't mean a whole lot to me >.< I'm not 100% sure without re-reading the whole post, but I think the method you described might already be on the list of things to try that I just linked in my reply to the above comment. If it's not, I'll add it to the list when I get a chance.
I have no idea which steps are the most useful/likely to work for the largest number of people >.< but everything on the list has apparently worked for someone at least x3