So I open Radiant and run the map I'm creating, and then I'll maybe make one room. Then it makes an error noise and crashes. please help. I do not want to delete a bunch of files and reinstall them.

Try running launcher as admin. It might be crashing during auto save.
Make sure your game install folder/bin folder and its applications (exe) are not set to "read only".
Also check the ugx wiki modtools install instructions to be sure you didn't skip a step.