It has been several years since I drove past Chicago.  My favorite route was Highway 51 (I think), west of Chicago.  Going south I would pick up 51 near Beloit, go straight south till I got south of Chicago, then back to the Interstates.  A good, fast road; the semi trucks use it and keep traffic moving at a good clip.  Last time I was on it, it was still just 2 lanes; so a little nerve wracking with traffic, no sightseeing while you're driving on it.
Do the ferries run over-night?  Perhaps you could get on a ferry later at night and sleep while it crosses Michigan?