Ok, I think the problem is only with the mods and not with EM4, as I put all of Fuchsburg's files with all the edits I made back into EM4, and the problems came back, and I just reinstalled Fuchsburg with the default files, and it went back to normal. That still doesn't answer why editing Fuchsburg caused problems with Wegberg (I didn't even open Wegberg's mod folder, let alone edit any of its files, I'm still really confused about that), and why reinstalling Wegberg isn't fixing it, but at least I figured something out. Sorry for double-posting.
I was just being stupid, it had nothing to do with Fuchsburg. I disabled UTF-8 in Windows language settings, and everything appeared as normal in Wegberg.