EU don't have to treat UK on "special conditions". Only if the output of UK destabilize the EU. Renegotiated trade deal comes into place if UK economy survive the coming crisis and next "credit crunch"
This is more complex. UK left UE and left the benefits of being in the EU. Germany is in EU. and trade with non-EU countries is valid for Germany, they can not treat countries outside the EU as well as countries of the EU. So German pay more for Nissan produced in England, the Englishman will pay more for a Volkswagen produced in the EU. This is not beneficial for both parties.
you're right, the EU will work with the UK, but the costs of this cooperation will increase (e.g in the form of customs duties) and charged to taxpayers
