I understand the predicament.
Sharing the backyard with somebody else might cause problems along the way, as free ranging chickens will easily turn the greenest and nicest garden space into some kind of military training ground, digging holes and pooping everywhere and ruining plants and...
Why would you want to submit them to such a life?
Would you be willing and able to provide a nice second coop of good size with an attached big and well structured run for the cockerels?
It would have to be situated far away and out of sight of the hens coop and run, or else the cockerels...
The BR is exerting his dominance over the NH mix.
Usually, separating cockerels or roosters from each other and thus preventing continuous contact and interaction, will lead to enormous amounts of stress in both, the separated and the one remaining with the hens.
The separated will try...
With only 4 hens and no possibility for more, you need to rehome one of the cockerels/roosters, as it would be abuse for the hens to keep them both.
The ration 1.4 is already hard on the hens, but 2.4 is not tolerable as each rooster will instigate the other to mate much more than they ususally...