I'm surprised that the OP felt the need to post this question as it's not exactly hard to find the answer.
Search for "Chicago" for your dates and select "Reward Nights" for the rate.
Sort by: Distance from destination
Scroll down until you find a property that is within your acceptable points range. First property less than 35k is Holiday Inn Express Hotel & Suites, a Chicago-Midway Airport at 20k
Click on hotel link, click on local area and see:
Subway
Subway Station Name: Chicago Orange Line Rapid Transit Train
Distance: 0.5 MI/0.8 KM SOUTH to Hotel
Complimentary Shuttle Available
Too far to walk? Go back to the search list and select the next property within your points range.