Ditch the agent. Sounds like she's more interested in her commission than your well being. What does she care if you get hosed by this deal. Your agent will have already collected her fee and she's onto the next person who takes her "advice".
It's one thing to be flexible on certain terms when there's cause to get a good deal done. For example, like some have suggested you or your agent could do the work to obtain complete to estoppel directly with the tenants. The NDA you suggested is also a compromise. Maybe collect some respected source materials that show you aren't crazy to ask for such documentation. It's often said that no one will care about your business as much as you. I think you're experiencing some of that first hand.
If you think the deal is sweet enough and the risk acceptable, than by all means proceed. But if you have serious doubts or the deal is already tight, then consider caution. Often in deals it's a judgment call about whether an issue is significant enough to kill the deal or not. You're in the best position to decide upon your personal comfort level.