The only thing I see as a problem is one of the bitches displacing the agression on Chopper.
My two bitches hated? each other now they seem to be getting along most of the time so I have about 5 years experience in bitch to bitch hate here. The bitches lived seperate lives till recently being allowed short supervised interactions with each other.
Sometimes when Nik and Jas would go through a pissy spell, whichever bitch was with Bear at the time would beat him up in frustration at not being able to get at the other bitch. They would never do more than leave a small scratch on his scruff, but they would take him down and pin him. The excitement of being mad at the other dog would entice a fight between bitch/dog, but he would always quickly back down and let the bitch cool off. That is my experience so far. And I never encouraged that behavior, whenever the two girls started to get barking at each other the situation would be changed so they would not even know the other dog existed.
I hope this makes sense it is way past my betime.
Good luck!