I can't figure out how to run the 1.12dev version, as the Curse page is 1.11.2 and the GitHub is even more outdated, where can I find the forge multipart cbe for 1.12?

As FMP isn't released for 1.12 you will need to grad a dev build from http://chickenbones.net/Pages/links.html under the 1.12 mc version, will run fine on 1.12.2