Tbh, both greater deamon wont bat an eye wether Makato dies or not. So william should just penetrate makoto cham with his spear, and battle it out wih the two since he has clear advetage both in power and defense
The greatest defence against demons is being a blank the second greatest defence is Faith. The powers of Faith are not affected by a null zone, William should move from simply acknowledging the Emperors existence to worshiping him to be a true nightmare for the forces of chaos.
When will william visit his family, considering chaos can now enter his universe(human normal)
Since chaos IS multiversal (Nurgle has poisons and viruses from other universes and is equal to other chaos gods)