1. I can't reproduce that, it only did it once for me, but may happen if the submit button is clicked twice. I'll look into disabling it on click so you can't do that.
2. It uses the post excerpt that WordPress generates, the problem with trying to use the full post is that it'd have to strip out all non-text content, and I'm not aware of a WordPress function that does that
3. I'll apply a fix for that so it defaults to a generic image for users with no avatar
The plus version would have resolved the avatar issue as it sends the user's email address in the API response so I can generate a gravatar, but the plus version can't be purchased on its own, it's only available in our Resources subscription. Also, MacRumors uses our older XPress platform, not this plugin.