The NDA bit got me ngl
Truth is this is an antagonistic negotiation oftentimes. You want to be paid more, they want to pay you as little as possible. There’s unfortunately no playbook, just advice and experience.
FWIW if they were that evasive I’d just say “look I’m not going to name an initial number, I’d like you to name a range.” But I’m at a somewhat senior level so I have a different experience than others might