Hey Michael,
I am really sorry for the delay of this reply as it is a weekend for us here.
It seems like this error is coming from your Facebook apps, can you try temporary revoke with your Facebook autoposting from backend > Easyblog > Autopost > facebook > click `revoke access` and see is it can delete those spam post?
If yes, you have login with your Facebook account which configured this Facebook app > setting > apps > search "which facebook apps you configured in Easyblog autopost" > Click remove apps link
After that access your backend > Easyblog > Autoposting > Facebook > Click "Sign in via Facebook" > Click next until everything okay.
Then try submit a new post and delete spam post see all is it working?
If the issue still persists, can you provide us with your Facebook access so we can help you check on this?