The lowest B fare BWI-DFW in February is a broken fare, the $1,144 cited by the OP.
DCA/IAD-DFW can be had as a B at $736 as a single fare component BA0RA0MQ.
Southwest has non-stops BWI-DAL as low as $52 - and no change fees - if the OP wants to be prudent spending OPM.