@Junru1
hm... I've never heard guest or host are charged for the alteration (modification) of the reservation.
Guest and host fees are the percentage of the nightly fee so if the reservation is shortened then the guest and host fees can't be higher.
Am I missing something?
Threatening with a bad review is called extortion and it is not allowed on Airbnb, if you have it in writing then contact Airbnb and show them and they will warn the host.
I am sorry you booked with such a bad host, next time be more careful and read reviews before booking, and if possible book with a super host.