You're a star. I renamed it MDRG (acronyms FTW!) and had it in a different folder, but when I did cd (change directory, for those unfamiliar with Unix/Linux terminal/command line) to the location and ran the same command "chmod -R 755 MDRG.app", it worked like a charm. For anyone else reading, I still had to enable the game in Settings > Security & Privacy > General because it's an unsigned app. But this method 100% works. Thanks!