1. To post the URL to users social wall, plugin uses FB API og.likes method instead of regular share. Unlike regular share, this method comes with a stock logo and doesn’t support param to change it. So, no way to change this.
2. Modifying the text it bit tricky. Each social network has its own way to handling this. For example,for FB you have to add FB Open Graph Markups to your page. Please refer Open Graph markup
3. I will rectify the Twitter issue soon and update.
In Oct 2015 Twitter has made changes to JavaScript Events like Tweet, Follow.
Now Events are triggered when a user invokes the action rather than after the action is completed. Because of the change, Twitter generates the event as soon as user clicks tweeter button which open the locker without waiting for the tweet action by the user.
Workaround is to disable Twitter in Locker setup and enable only FB and GPlus.
