[Henry Schmidt]

In the OPs original statement , he states that the tenant in question (new) only had 3 month left on his lease so if he truly needed more space it can be argued that he would have left the complex at the end of his lease seeking a more appropriate (larger) location. Landlord would still have an empty unit if the OP decided to continue his lease.
If the landlord forgave the remaining rent on the small unit in order to entice the "new" tenant to take the larger unit, the OP owes nothing. Forgiveness for one is forgiveness for both.

The judge can seek a just resolution or just listen to the best argument. Either way, it's a crap shoot.