An itin like DFW - ORD - IAH - ORD - DFW at the dates mentioned gets a price tag of ~ $470 on CO.com. This route is perfectly legal. A roundtrip IAH - DFW - IAH on AA is about $200, total of $670 - still saves you quite an amount of money and gets you full CO mileage for the trip (and more since you connect in IAH from/to DFW). You can save the $200 by driving to Dallas (3-4 hours?).

I got the same pricing for AUS, a little more for SAT.

Also, as the last DFW leg connects via IAH you can skip the last leg and stay in IAH. This is not very legal but doable. The trick here is to schedule it to the last flight IAH-DFW, miss the flight and show up at the gate after the flight has left, saying you must be there tonight and would rather drive it than stay a night in IAH. This trick is not possible if you check luggage though.