Ok, first take a breather. CAD packages are not the easiest things to learn and all of them have their quirks, once you take first few steep steps up the learning curve it gets easier.
I can’t quite build complete picture of your situation but my best guess is that you have global library table pointing to missing lib files. That is one of the files (along with some configs) that is not deleted with uninstall.
To fix that simply go to Preferences->Manage Symbol Libraries... in eeschema and delete the libs that don’t exist any more.
After that it’s just matter of fixing your projects if they still have parts from those libs. When opening that project you will get a symbol rescue dialog. Read this faq entry carefully, that describes what’s going on there (option 2 is most relevant)
In case you still want to go full uninstall route: after running uninstaller delete kicad folder in %APPDATA%/Roaming on windows or ~/.kicad on linux. That should get rid of everything I think.