On the ICS keyboard the enter key turns into the smiley key in the messaging app and I can't go to a new line.
How do I get the enter key back or add a new line to my text messages?
Can't be done... that's how the ics keyboard is setup. You can either send bursts/multiple messages or either change to a 3rd party SMS app or keyboard.
Something like GoSMS Pro, Handcent SMS or Swiftkey, SmartKeyboard Pro for example.