I have a few that I'm weaning off this week, and I still have your 1.2 held back

I wouldn't recommend splitting the tank, ASFs get extremely territorial after they mate, and will (at least in my experience) kill any newcomers, male or female. I've tried introducing new males or females after cleaning the tubs to no luck either. The only way I've been able to successfully add or change the demographics in a tub was to grow up one of the pups to join the crew.