Once in a while, I check my Recent Activiy on Facebook. and it says I played a certain track. My Preferences for Sharing my activity and what I listen to on Facebook is also off. What's the deal? I listen to music half of my waking hours everyday.
Since it looks like you have already done all the steps necessary to turn off sharing,
I suggest you contact support so they can take a look at your account and see what is going on: https://www.spotify.com/about-us/contact/contact-spotify-support/
If you get an automated reply email, you need to reply back to it.
Support usually replies within 24-48 hours.