Finally, a nit to pick: Southwest is not going to want to a link to DFW, as they operate out of Love Field. If anything, a direct Dallas link will face tooth-and-nail resistance from Southwest.
So, what, have the HSR line go from Dallas Union Station via the Green Line's alignment to serve Love Field, then take the Orange Line's alignment to serve DFW?
Sure, except that isn't a high speed alignment, even if you build new tracks.
For Love Field, the best option for HSR-to-Plane would be extending an automatic people mover to the Green Line's station, followed by a direct train ride to Union Station?
And for DFW, extend Skylink to the Centerport TRE station, then have every other HSR train between FTW and DAL stop there to serve passengers?