google AirBnB customer service, call them, and take notes
I have more experience with AirBnB customer service than most FTs - so I will take this one.
You made a big mistake by staying in the substandard accommodation. I walked away from one in Jersey City and AirBnB found me something better - no upcharge.
I did the same near Osaka and opted for a full refund. Having said that, the key was having pictures I could send them. Otherwise, I am not convinced the outcome would have been as good.
I am now locked in a dispute with AirBnB about a host no show in Duluth. The replacement hotel was expensive and I want AirBnB to cover the difference.
My suggestion is you google AirBnB customer service, call the toll free number and take notes.
The weird thing about their policy is AirBnB expects you to deal 1st with the host. What is the host going to say? Of course, they will deny, deny, deny.
Persistence and patience is my best advice.