Agree with above posts to stay on I80 past Chicago plus take I380 up to routes 218 and 18 to join I35 in northern IA to I90. We came home that way in 2012 after a stop at the Winnebago factory in Forest City IA.
Another route option for your consideration. When heading west in 2012, we took I80 across PA to Youngstown then I76 and I71 to US 30 at Mansfield OH. US 30 is a divided highway all the way across OH and IN and joins I65 just south of Gary IN. It's about 20 miles longer than staying on I80, but avoids all of the tolls in OH and IN.