Yeah, whitespace doesn't really matter, as long as it starts on a separate line below the one commented out with the hash (#).
I'm sorry dude, I don't know what's going on there. Something is preventing the script from making changes to your system, I'm guessing some level of security in the OS. You might try running the script with admin rights (sudo sh run_bepinex.sh), that might do it if your user account just doesn't have sufficient rights. You might try moving the folder somewhere else if it's currently somewhere that might be more protected, MacOS has several folders that are protected by default. I have mine running in a folder under /Users/[username]/games, but it's also worked for me in a folder on the desktop. You might look at system settings to see if there are security switches you could try modifying or disabling, though I'd strongly caution against making any permanent changes or running anything else other than this BepInEx script with security lowered or disabled. (Once the script runs initially and creates its folders, it shouldn't need to make any other changes to the filesystem. It'll try writing that log file every time but as long as it works, you won't need the logs.)
Maybe someone else will come along with more or better ideas, but I think we're in a pretty narrow subset of users already (interested in this particular game, running it on a Mac with this particular architecture/OS, trying to inject a mod not really designed for this architecture/OS with a hacky workaround). If I think of anything else though I'll post it and tag you.
thanks for your help
