Is there any limit (besides the OS files system limit) on how big the db file size can be with SQLite?
Mostly it's operating system limits.
Also, is there any NFS locking issue with SQLite database? Sometimes if a client opens the files and die, do we have problems reading the file again because NFS lock for the file still exists!? Is this true?
Yes, some NFS's don't do locking very well.
