I can't share a copy of the repo, but I'm going about introducing FFI the opposite way: pick Arc 3.1 and add any files that are needed to get just FFI and mysql-ffi.
That's a good approach. Keep at it, I'm sure you'll figure it out.
One way to get help with it: describe simple step-by-step changes to the repo that cause errors. Download arc 3.1, add this file from here, type this in at the repl, etc. Don't forget the actual text of the error you see as well.