My first question is that ‘of course’ this new 7 days does not apply to people that already booked. Now that would be a game changer. I doubt is the case, but worth checking.
I know one thing, I will call and instantly insist to talk to a higher up, leapfrogging the ‘gopher’, or write directly to a supervisor, if that doesn’t make sense to him that the new 7-day/50% cancellation ~surprise~ change is absurd in my case, then we do have a problem. Last resort, I will contact my personal friends at AirBnB to take the message directly. Super last resort, I will give emphasis to other booking services. Airbnb I have found are quick minded, it wouldn’t get past stage #1.