Your front 02 sensor only has 25k on it, and that in itself sounds too young to fail, but since you had so many other things done to the car, perhaps the other issues led to early failure in your front 02 sensor. Bcuz, if this misfire under load problem is only happening when the car is warm..........your symptoms are classic front 02 sensor signs. My front 02 sensor needs replacing every 40k miles like clockwork. 2001 Forester with 112k on her.
I say replace it, and report back here.