You almost certainly won't punish it effectively, and you run the very real risk of making matters worse by trying I'm afraid.
I'm not sure if you've ever just walked off, but it would be interesting to see what happens and would give a clue about the problem. Obviously if anyone is at risk of being seriously hurt it is better to break them up, but if it's just pinning to the ground then walking off might be your best course of action.
In any case, getting in a behaviourist now would be money well spent. How you handle sudden changes can have a big effect on the situation and a behaviourist will be able to assess your dogs and make informed recommendations.
Yes, when I pull him off he goes in harder.
I have walked out of the room and called him in a cheery voice and he continues for a short time, then comes after me.