IANAL

Your landlord did not “let you off the hook,” the landlord offered to reduce the rent to your other roommates in order to facilitate a new contract agreement so that the two remaining residents could complete the lease. If they refuse to do that, for whatever reason, the initial contact still stands and you would be responsible for the portion of the rent that you agreed to pay before your circumstances changed.

The landlord does not have to eat the cost of your life circumstances, and neither do your roommates, who, unfortunately, appear to be willing to fight this all the way to court. Your only course of action now is to document all of the ways you attempted to negotiate with them, and to save evidence (not just verbal) of your landlord attempting to accommodate and negotiate their rent. You’ll have to prove that they acted unreasonably, or that your living conditions were not what was agreed upon, because yes they can just refuse to pay your portion of the rent or sign an amended lease agreement without you.