You'll never do a 1hr inter-airline (between Southwest and Seaborne) connection with checked luggage. At best you'll need 15 minutes to deplane and walk to the baggage claim area, figure another minimum 10 minutes wait time to before your luggage arrives on the carrousel. Add to that another minimum 20 minutes to check in for the Seaborne flight and 30 minutes to clear TSA and walk to the Seaborne departure gate. That's a total of 75 minutes (assuming all the stars align) and you only have 55 minutes. You need to "manufacture" at least another 30 minutes to even think about making an inter-airline connection.