[NJ] Vacated residence early at request of Landlord after paying entire month rent- am I due a refund?

NJ, Monmouth County. Moved out of residence in question over Thanksgiving and notified Landlord. Lease was through December, so I told him December Rent would be paid, but if he found another renter to let me know and I would release possession for a refund. Landlord later texted December 14 stating he had a Certificate of Occupancy inspection scheduled for Dec 21 and wanted to know if property would be vacated. He asked that he be texted when all items were removed that we had vacated and given up possession. I sent that notice after collecting a few final things and a final clean on Dec 18 and he acknowledged via text.
Received security deposit refund today, receipt noted we vacated Dec. 18. I texted Landlord asking if refund would be on another check; his response was there is no additional refund. Rent was $1550, I figure I'm owed $650.
Small claims court, or forget it?