I just did the Schaumburg to MDW run with a co-worker last Friday night in the rain, leaving at 4:10pm. We rolled up to MDW about 5:45. and that was in Friday night inbound traffic, with rain, so pretty much the worst of all situations (plus I went cross-country from I-290 and Mannheim to MDW to avoid some jams and keep moving). In theory, you could make the run in about 60 minutes if there was no traffic. The preferred route for me would be I-290 to I-294 South to I-55 North, exit at Cicero Ave. Problem here is that the ramp from 290 to 294 is awful in rush hour. Everything else isn't too bad, although I-55 can be slow -- an alternate would be to exit I-55 at First Ave. and follow that around to Archer / 55th Street. But the First Ave. bridges at I-55 are now messed up. Welcome to Chicago...
GPS and various maps will say I-290 to Cicero Ave. Problem is, the 290 from Mannheim to Cicero can be ugly at any time of the day and I'm not sure that Cicero Ave. is a picnic.
I went cross country only because I know the area and my time included some slow residential areas and a major delay on First Ave. over I-55.
Bottom line is that I would never recommend MDW to Schaumburg unless you can plan to travel mid-day. I told my co-worker that his time is much more valuable than the little bit of savings on Southwest.
As someone else noted, you could drive to ORD and grab the Blue Line into the city, then jump off at Clark and Lake and transfer up to the Orange Line. Not sure that it would save much time, if anything.
The one nice thing about the DL / NW merger is that you do get a lot more options if you don't mind connections. Granted, a connection in ATL or MSP isn't very much fun, but think about the miles and segments... this is FT after all!
Is JFK - ORD an option?