Generating keyhashes is complicated, but possible. I managed to do it without getting an error using the Command Prompt.
Where I gave up, was getting the publish_actions permission from Facebook required to have users post links and messages. Since a recent policy update, it is no longer allowed to have an app write a custom message (even if the user can edit it afterwards). That was the first reason my submission got rejected.
It was fine though, because you are allowed to customize links, descriptions and captions so I'll just use that.
However this was my second rejection (where I just gave up until an update on the extension):
Your app cannot embed the Facebook Login dialog inside a custom web view. Utilize our native Facebook Login SDK, so that users do not need to login twice.
So this is as far as I got with all this.