I go to every game, and when I don't have tickets, I just wait until near kickoff, and I always get tickets. Every single time. And the most I had to spend was $20 (35 yd line, lower level), for Oklahoma, and I think that was only because I didn't wait long enough, I just wanted to get inside and see the boomer Sooner stuff and all that. I got into the Stanford game in 2012, the game where GameDay was here, for $7. I missed the first drive, and the rain helped drive the price down I'm sure, but hey...$7.
And I always get them either in the parking lot on my way from a tailgate to the entrance, or right by the entrance. You can't miss the scalpers.
Now, the caveat is...I've never done it with my kids yet (too young), and I've never had to do it for a night game. I always get my in-laws tix for those. With 2 night games, I chose the USC game this year, so I will be in the same boat as you for the TX game. Should be interesting. I'm not telling you to wait it out until the day of the game, because the way I deal with the stress of not having a ticket (doesn't really faze me) might be WAY different than the way you do (my wife can't handle it, for example; she gets beyond nervous). I'm just telling you, it has been an option for me in the past, for day games. I just sold my in-laws tix for face-value to a buddy, but if I come across a pair (REALLY hard to find right now), I'll holler at you. Good luck!