The fastest route from Dallas to Chicago is US-75/US-69/I-44/I-55. The halfway point is Springfield, MO, which has a good selection of budget hotels at Exit 80. I have personally stayed at the Super 8 and it's acceptable.

Tolls will be $2.00 on I-44 in OK, pay cash. There won't be any tolls in Chicago if you take I-55 into the city. Note that there is NO inexpensive lodging anywhere near downtown Chicago that would be safe.