With the tush push being so effective, they effectively only have to get 9 yards every three downs. So what kind of advantage does it give them
They currently convert 76.5% of their 4th downs, compared to a league median of 50%. Regressing them to the median would result in 4.5 more failed attempts. They average 2.54 points per drive, so 4.5*2.54 = 11.43 points on the season, or roughly 1 point per game. According to Vegas, a 1 point shift in point spread averages out to a 1.3% increase in win probability.
So about 1.3% of an advantage.
They also run the play on 3rd down a lot and they run it at the 1 or 2 yd line regardless of down sometimes. It is definitely a lot more valuable than your brief 4th down analysis. It pretty consistently sustains drives that would have otherwise had a much higher probability of ending sooner.
