I had a similar problem to #1 on (I believe) a website that required an account to use. I created one using Facebook, was able to login using Facebook, but couldn’t delete my account using Facebook. I had to remove the app from Facebook and delete my account on their website. And when I attempted to delete my account on their website, I was required to provide a password. What password? Luckily, I was able to request a “new” password and delete my account, but was still annoyed by the needless step.