@Camilo51, as @Lawrene0 mentioned, it does not matter at all that the host changed their cancellation policy. Whatever cancellation policy was in effect at the moment your booking was confirmed is the cancellation policy that covers your booking.
Plus, I don't think the host has any say in how much money you get back. If you do a cancellation, AirBnB will handle refunding your money. The host doesn't have any of your money yet anyway.The only time AirBnB ever asked me as a host about a refund was when AirBnB asked if it was okay to give the guest MORE than they were due. (It was.)