It is 142 miles according to Google Maps.
Google Maps estimates the driving time as 3 hours and 5 minutes.
Houston is much closer to Austin than Dallas.
Take I-10 WEST from Houston all the way across to U.S. 285 to PECOS and SANDERSON off EXIT 257 in Ft. Stockton. To bypass SAN ANTONIO, take I-410 NORTH (& WEST). (EXIT 581 off I-10 to get onto...