Did you physically remove the fleas with tweezers to get them off his body? If not, he will not recover as quickly.I do have used pernethrin. I have noticed significant decrease in mites within 24 hours . But my rooster overall is even more weak now. He can barely stand when made to stand . Walks a few steps and then again down to ground. One thing u have not3d that he is eating and drinking enough and his poop is fine as well. He is heads down and sleeping all the time
He may also be suffering from anemia hence the recommendation for lots of water and protein to build him back up.