I don't think that the Swiss Lounge is going to be much use for you if your flight leaves at 12 from ORD T5.
In May 2011 the hours were as follows:
The SAS Lounge closed at 9:30 PM on Thursday nights (open until midnight on Friday and Saturdays due to flight timings)
The Swiss Lounge was only open between 2 PM – 5 PM (timed with LX flights)
TK business class / first passengers used the contract Swissport.