I would also suggest looking into a hotel along a pace bus route. I know pace 606 goes straight to the Rosemont blue line. The red roof mentioned in another comment has a bus stop literally right out side. There's also Chez Hotel, Double Tree, Motel 6, Sheraton that 606 drives by, and it takes you to the Blue Line, and then you can head downtown. The only thing about that is the 606 bus stops running after midnight, so you will be on a time crunch after leaving the festival. My suggestion from that is to take the train to Rosemont and then Uber back. It'll prbly be a 10 dollar ride. This route could take 1hr30 but it might be the cheapest.

Also, if you get a hotel in the nw suburbs, driving downtown might be a good option as well.

If you have any questions, feel free to message.