Work with the realtor regarding the CFK agreement. Typically you'll be allowed 30 days or so to move, and they'll offer you at least $500 to cover your moving expenses. You can either accept what they offer, or ask for more.
Being a non-owner does not change your rights in this situation. The bank is now the owner of the property, so you'll need to negotiate the CFK with them in order to extend your time to locate a new home.
First let me say how sorry I am to hear that you have lost your house.
You should continue with your negotiating for the cash for keys. In our area they usually settle for around $1200 give or take. They will initially offer you a low sum, like $500. You should also negotiate for time too, 30-45 days.
Once the agreement is made and signed off on, that is the time you will have to move.
The legal aspect, the 3 day notice to move, runs in parallel with the keys for cash negotiation. This is so if the negotiations for the keys for cash does not work out, the legal remedy is already in motion.
Once you have completed the keys for cash negotiation, and signed off, the other legal measures are put on hold.