Sorry to hear about your situation, I know how you feel. Unfortunately I am not really au fait with the type of situation that you are in, but as far as I am aware if you don't accept the conditions then your contract is terminated from their side, and not a mutual agreement.
To be sure, there should be numerous sources for legal advice nearby (or at least in the main city of your canton. Usually unions and the Arbeitsamt offer legal advice on a no-responsibility basis).
You have just reminded me to update my thread, as the matter is still dragging on...