Contact a professional architect or building engineer. Don’t play with this kind of stuff yourself in NY; you can lose everything.
In fact, when I had yechidus with the Admou”r meCreedmoor, he told me that if you set your house alight, you will not be able to collect insurance on the illegally extended part.
Seriously, violations of any type are serious business. Don’t touch a home or building with uncorrectable major violations. Sometimes an architect can correct them but fines probably have to be paid along with steep planning fees.