1 - No, not really, short of changing the FTP server. VMS has mandatory file locking, so the only way you could get the file is to have the server open it in read-regardless mode. You might check the FTP server's documentation--it's possible you'll get lucky.
2 - Net::FTP subclasses Net::Cmd. Try the message and code methods and see if they give you anything useful.
3 - Have the job create a flag file on completion, and check for its existence. If it doesn't exist, the job's not done. Or just have the job e-mail its files to you, which is pretty simple. Or have the job FTP the file to you--perl and Net::FTP work fine on VMS. :)