For a simpler installation procedure of BTW and its addons, consider using the MultiMC launcher (BTW+fabric profile).
This installer can be used to generate a Cursed Fabric for BTW profile in the vanilla launcher and to setup a server, while also supplying the required fabric-loader jar (see this repo) automatically.
THIS INSTALLER DOES NOT INSTALL BTW, ONLY THE REQUIRED LOADER!
For instructions on how to install BTW after this, see the instructions for vanilla launcher.