I would avoid Dallas if possible by using I-69/US-59 or leaving I-45 at Fairfield and going up through Athens. Google Maps says that route takes 6 minutes longer, which the Dallas route could easily use up with one traffic problem there. As others have mentioned, the stress will be a lot less. I have started literally going out of my way to avoid big cities while towing a trailer. I find big city car & truck drivers are not very considerate of RV's, often to the point of being dangerous. Check out the alternates on Google Maps.
one_strange_texan
Currently between RV's
Former 5th wheel owner (Montana 3402RL)