I don't know much about Trans States other than what the internet says, but I do know that ORD - STL is not an easy commute. With the influx of old TWA people into Eagle and AA that are forced to commute from STL to ORD it is very hard to get a seat. In fact, it's quite common to have a 2 leg commute from ORD to another stop on AA then connecting to STL on AA connection.
If you live in Chicago, then invest some $ and get on Climbto350.com and check out the weekly jobs posted on there in Chicago or get hired at Eagle, Skywest or someone based in ORD.