Near closing on a short sale with a tenant that wont vacate. What are my options if...?

I'm in escrow and near closing on a short sale. Only recently while doing the final walk through do I discover that it's not the seller living in the house but a tenant that's refusing to leave. And $8000/5 mos behind on rent by the way.

In our contract the property was to be vacant 5 days before close of escrow, a bridge we were supposed to cross on 9/14 however my agent and lender are helping me to delay closing as much as possible. But the seller is now in breach of contract.

Finally today the seller served the tenant a Notice to Pay Rent or Quit but I'm afraid they won't have them out before it legally becomes mine. I'm sure we can only stall so much longer. So...

1A) Should, god forbid, the tenant still be there when I take possession, do the actions that the current owner are taking against the tenant still stand? Or am I starting at square one?

1B) What will I need to do?

2) I was going to be out of my apartment Oct 1 but now will have to pay rent for another month or so, utilities, etc. while this is taken care of. What options do I currently have against the seller for being in breach of contract?

I know, I jam packed a lot of questions here. Thanks!