You say "Texas has beat KSU" but they haven't even played yet, and the only way ISU is at risk of not going to the championship game is if KSU beats Texas. I remain curious what happens if West Virginia, Texas, and KSU all finish 5-4, as it seems to me WV wins that tie breaker to finish 4th, which knocks ISU out of the championship if ISU were to lose and OU/OSU win out. I still don't see how a Texas victory over Kansas matters at all.
3-way ties aren't resolved for the purpose of determining tie-breakers with other teams. In other words, if KSU, UT and WVU all tie for 4th, you would compare our round-robin record against those 3 teams with that of OU/OSU. We would all tie, again, at 2 - 1 against that group. You would only resolve a 4th place tie if it was a 2-way tie, and you'd compare all of our records against the winner of that two-way tie (WVU).The reason the Kansas/UT game matters is because Texas would be 4-5 with a loss to both KU and KSU, making WVU the winner of the 4th place tie with KSU. If Texas beats KSU, then their game against KU no longer matters. They need 1 more win to guarantee them a share of 4th, which would guarantee us a spot in the championship game.
Read section b, parts 1 and 2.
Tiebreaker Procedures
big12sports.com
In the event of a 3-way tie for 4th, the championship game tie breaker would come down to score differential between the 3 of us, because none of us have lost to anyone else outside the top 6 teams. Because OSU got stomped by OU, they'd be the odd man out.