I believe FastDL is working like it should now as it downloads when I join the server, but the custom models still appear as errors ingame.
On my FastDL webserver and on my resource.lua, it has maps, models, sounds, resource, materials, and particles.
Webserver: http://trinityrp.x10.mx/gmod-dl/ (Ignore the extra folders)
And yes, I also moved all my addons to the appropriate folders on the root.
Edit: The above works now, but I got a new problem, see below!