How to reset iCloud music library when reset option is missing?

I have spent hour and hours trying to fix the disastrous state of my music library in iCloud, to which corrupted tracks were inadvertently added after updating to iTunes 12.2 awhile back. I now understand that I need to reset the iCloud library from the main computer on which my complete local music library is located. But yesterday, following instructions I found here - If your music library shows incorrect details with iTunes Match or Apple Music, and you previously cancelled an iTunes M… - which said to reset from any computer, now I cannot reset again because the reset option has disappeared from the iTunes account tab. So I have a clean copy of my personal music library, but when I turn on iCloud music library, that just gets merged with the bad tracks that are still in the cloud. To clean it out manually, I would have to listen to and then remove more than 2000 tracks. So: does anyone have a step by step on how to reset the iCloud library in the absence of the option of the iTunes account tab? I've seen a couple on non-Apple sites, but would prefer guidance from the support community.

I'm using a MacBook Pro late 2011 that runs OS X 10.11.1, El Capitan.