I tried using Chrome's Dev Tools to go through your code but seems as though it's been minified so I didn't bother trouble shooting. Instead I'd suggest a work around, that may solve your issue.
Consider using jquery's trigger event to trigger a "keydown" (see top answer in Definitive way to trigger keypress events with jQuery). Now I've tweaked the code around a little to perform the action that you desire.
In the HTML mark-up you'll have your input field as well as the button:
<input type="text" name="blah" />
<button id="clickme" type="button">Click Me</button>
And in the Javscript, add a click event for the button with a function that triggers the keydown press for the "return key" - like so:
$("#clickme").click(function(){
var e = jQuery.Event("keydown");
e.which = 13; // # Some key code value
$("input").focus(); //to ensure that the input field is in focus
$("input").trigger(e);
});
That should do it, the button should replicate the keydown press of the return key on your input field - so you don't have to worry about tinkering with any of your current functionality in your code.
By the way, used this link to get the character code for "return key" - it has a whole list of codes for other characters http://www.cambiaresearch.com/articles/15/javascript-char-codes-key-codes