My understanding is as long as there is a seat then with a companion pass you get to take it. But is it possible to add a companion when the wanna get away fare is not available 7 days prior to departure? I don't think it matters if that fare class is available or not right?

Also, when they are down to the business and anytime fares, does it mean there's 10 or fewer seats left? How many seat remanins usually for them to stop selling wanna get away fares? I'm sure it's different with each route but a rough idea in terms of number or % would be interesting.