Chu Yunsheng has never seen Ning Zhitong's real power before, so he did not know if Luo Hengshen and Cao Zhengyi could stop Ning Zhitong from escaping or not. He just hoped that they could stall the man until he sorted out of the bomb problem.
Originally, Luo Hengshen did not want to fight Ning Zhitong. Among them, Cao Zhengyi was the castellan, so he should be the one in charge of this. However, before Chu Yunsheng ran into the food storage, he ordered him specifically. So he could not avoid this fight.
From the information Luo Hengshen had about Ning Zhitong, he believed that Ning Zhitong should not be more powerful than him. However, he had the fire messenger's sword, so although he might not be able to kill them, there wouldn't be a problem for him to stall them there.