In 14.2, you can just right-click the app(s) or action(s), choose "Change connection" and pick another connection from the login window. No need to open each action or even make a connection if it's already in the login window. This is a completely new feature. It did not exist in 14.1, even for single select.
For #2, can you just do this to choose an existing connection? (I know, not every type of action has this toolbar item).
Maybe this is a good time to get the beta. 
Toad for Oracle 14.2 Beta