Is LGA an option? Found on Google Flights:
UA:$177 LGA-ORD rt 1000PQM (w/ 500mi min)
Tue 15 Dec
UA569 LGA-ORD 0600-0736
UA698 ORD-LGA 2015-2325
http://goo.gl/flights/XEo1
I also see it on the next day. First and last flights, hopefully you're currently Gold and can SDC to a shorter pair.
Perhaps not the most comfortable option, but best price I found so far.
A bit outside your date range, but EWR-CLT rt is $153 on Dec 29. (Without SDC privileges, you can book the 1154am return for $16 more.)
Good luck!