When Wallman got hit, people commented he vomited out Cement and wondered what his body is made of. Also, the message from Braveman phone is that the broadcast is pushed forward for 1 hour 30 mins, that is why they have to rush it.
The reason why the leader decided to stay and fight Impact is because he mentioned the boss power is brainwashing so it is most likely he will target leader and use his power to defeat the villain league so this is the only chance he will get to show off his power. He said if RX leader got brainwashed then the situation isn't that bad because he is still here, that is why they let them go first.