I don't think it will, no! You've added a Cron Job in the FreeNAS GUI and not inside the plexemail jail. Don't think you can run a jail Cron from the FreeNAS GUI which is why I showed the steps to create one inside the jail (although I don't know whether it works yet!)
Not sure about the website. I get the plexemail webpage by just typing the jail IP address into a browser (e.g.
http://192.1.1.32) but I've got no intention of exposing that outside my network. If that brings up a blank page, you could try
http://192.1.1.32/plexemail (where 192.1.1.32 is your jails IP address) but other than that I have no idea. A blank page suggests to me that Apache is doing what it should, otherwise you'd get an error message.
Maybe a question back in the plex.tv forum?