Can a trustee, who has been paying the taxes and homeowners insurance on the house in trust, legally stop paying those bills?

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It depends on what the trust itself says. Is there a life tenancy for the current occupant who is likely to be the grantor of the trust? are you the trustee or the grantor/trustor? Was it your house before it was placed into the trust?

Not sure what error the attorney did - If the house was put in the irrevocable trust - it is the owner, and in its control, so the trustee would have a duty to pay the taxes and insurance unless the trust provides otherwise. with irrevocable trust, it takes away the asset and control from the grantor/settlor. So if you did this - you probably have a life estate interest and most life tenants do pay taxes and insurance and maintenance. Again the terms of the trust should answer this. May want to let another NY attorney review everything and review the amendments. Sometimes the irrevocable trust has limits as to amending it.