Unix stat()/lstat() for Java
Looks like you've pretty much covered all the bases. When I started reading your question my first thought was JDK 7 or JNI. Without knowing anything about the change pattern on these files you might also look into some sort of persistent cache of the information in question, like an embedded DB. You could also look at some other access method besides NFS, like a custom web service that provides bulk file information from a remote host.
Yes, stat() is under all the calls and libraries. It is a latency problem. However, you can do many stat() at once, as there are many NFS server daemons to support your connections, using threads unless someone has an asynchronous stat() up their sleeve! If you could get on the host, like with ssh, stat() would be much cheaper. You could even write a tcp service to stream in paths and stream out stat(). Unfortunately, access to the NFS server is hard or impossible, as it may only have admin accounts, be a Hitachi SAN or something.