@Jacqueline668
Uh, sorry for your trouble 😞 Your host obviously forgot to timely adjust his price for this event but this is not the excuse and is not your fault. He should honor your reservation anyway.
There is nothing Airbnb or you can do to force someone to host you against his will.
Airbnb can cancel your reservation on your host's behalf, charge them 50$ for cancellation, block those dates on his calendar, give him automated bad review or delist him from Airbnb.
But, as you said he has already listed on another booking platform and will cover his loss with a higher price.
Anyway, you should not cancel from your end or you will lose service fee so be persistent until Airbnb doesn't cancel this booking and refund you all the money.
Here are different ways to contact Airbnb
https://community.withairbnb.com/t5/Help/Contact-Airbnb-A-Community-Help-Guide-UPDATED/m-p/413245