New
#11
Removing your current iTunes and installing a previous version is part of the solution to use less resources, and stay on a version that works for you.
Keeping your music library is a different matter. It works pretty well while upgrading, because newer versions can read older libraries, but this doesn't work the same way going back in versions. You might want to import all your music from scratch, OR, you might want to install your previous version (compatible with your library) and then EXPORT your music library. This will create an XML file that you can import on a different iTunes version with the "import music list" function on the same area (file menu).