I saw this about a year ago and thought it might come in handy. I haven't used this service myself, but you could check it out.
I would also suggest try calling the office of the city council person in your old district. They usually have some sort of housing expert on staff.
The New York’s Housing Stability and Tenant Protection Act of 2019 contained a provision to make it easier for tenants to get out of leases by finding a replacement. I think this is what Chicupbeat is referring to above. Seems to me your old landlord is being unreasonable and not following the law.
Here's the wording from the law:
Duty to Mitigate
Damages by Renting
Apartment
RPL § 227-e
• Landlord must in good faith, according to landlord’s resources and
abilities, take “reasonable and customary” steps to rent the apartment;
residential only; commercial leases and licenses not affected.
• Overrules Holy Props Ltd, L.P. v. Kenneth Cole Productions, Inc., 87
N.Y.2d 130 (1995).
• Lease provisions to the contrary are void as contrary to public policy.
• The person seeking damages has the burden of proof.
• Effective 6/14/19.
Here's a link:
https://nysba.org/NYSBA/Online%20Con...tectionAct.pdf
Best of luck!