Thanks for reporting this.
It doesn't seem as if the upload of artwork has succeeded. You can see in API response that artwork-url
has nil=true
and no actual content – http://api.soundcloud.com/tracks/71930639?client_id=YOUR_CLIENT_ID
My suggestion would be to re-upload the artwork again and then do the facebook lint trick you were doing.
As for the second issue, maybe this link will help.