Never had any problems with vivid seats or stubhub. Although the handling fees seem to go up every year. In my personal opinion, FF row 5 are great seats. But you're asking someone who has probably sat in the lower bowl only a half a dozen of times in the last 40 years of attending UT games.
Vividseats is safe and is probably the "cheapest" 3rd part seller, though be prepared to pay a ridiculous fee on top of the ticket price (regardless of what ticket site you use)
