I just tried this on my 10.13 Mac and it seems to work just like it should. I'll send this out to a few of the teachers who were hoping for it and see how it goes on a few other macOS versions.
Yeah, I am seeing similar things with the download. The version on my MBAir is working fine, but installing the various SDL frameworks via MacPorts puts symlinks out to the /opt/local/ folder and my programming skills aren't very current. I was hoping that just dereferencing those symlinks would do the trick, but apparently it didn't. So, back to the drawing board I guess. I'll keep looking into this and see if I can come up with anything.
I am not one to know how to update the actual project, but here are the four needed SDL.framework files. I just created then using MacPorts. I compressed them and dereferenced the symlinks, so this should be complete for those looking to update their app.