This isn't quite an answer, but perhaps a perspective/option. Our library hasn't been able to get NYT to do straight-up IP authentication and for years they have been a challenge for us.
Recently, they rolled out an educational institutional access option. Through that option, our users must sign up for their own account, which is associated with our account based on their having signed up for the account from a computer bearing a campus IP address. The actual access is based on the password they set up for their account, and they can use that password from anywhere. But to get the password, they have to be on campus.
It might be worth asking whether some kind of hybrid solution might be available, using IP access for inside the library and using password/account based access from off-campus.