@Milo351 Instant Book is turned on by default when you set up a listing. You have to turn it off in your settings if you don't want to use it. And if you do use it, you can set requirements, like govt. ID and previous good reviews.
I'm not sure what you mean, you could turn a guest away at the door. You can't turn away a guest who has a valid reservation, of course you'd be penalized for that. The only exception would be if the guest arrived and was extremely drunk or drugged and/or belligerent. Or wasn't the person listed on the reservation.
You can't expect Airbnb to deal with situations like the one with your current guest. Even if Airbnb called the guest and told him he had to leave, how are they going to physically enforce that? That part is up to you. When a guest's reservation is over, they are then trespassing if they won't leave. So they need to be dealt with however any trespasser would be.
Depending on your local laws, letting a guest continue to stay past their reservation dates, because they are in financial straits, or keep saying they'll pay you "tomorrow", could mean they end up being there long enough to claim tenants rights.
Having empathy for others is wonderful, but not to the point where we allow them to take advantage of us.