DFW does not have a CRJ base, only ORD. As an FO, you would be stuck in ORD if you chose that aircraft. The 145 has a base in both ORD and DFW, so if your goal is to get back to DFW, choose the 145. As to how long, I can't answer that. My guess is a couple months at the most if hiring is robust, if it isn't, then it could be awhile. It all depends.

The commuter policy supplies you with six commuter issues per year. You need to attempt two flights before you are covered. Keep documentation, i.e. Boarding passes, PNRs, and so on. You will not be paid for any flying you miss, however, if you choose, you can use vacation days from the next year to cover any loss of pay. If you are caught in traffic on the way to the airport, the chief pilot may work with you at his discretion. It happened to me once when I was LGA based and it was all worked out.