/opt/kaltura/nginx/conf/kaltura.conf.template is part of the kaltura-nginx package, the fact it isn't present will cause issues, understandably..
What's the output for the following commands on your machine?
# dpkg -S /opt/kaltura/nginx/conf/kaltura.conf.template
# dpkg -L kaltura-nginx |grep kaltura.conf.template
If the file is not present, try aptitude reinstall kaltura-nginx
As for the other question: yes, when using the Nginx VOD module for delivery, Nginx must be accessible from all machines playback should happen from. The player will be making requests to Nginx to get the manifest and segments.
You can choose any port you wish for it during the configuration phase and you can also use a LB accessible to all clients and balance between Nginx nodes who are not accessible to the outside world.
When taking that approach, you will need to modify the DB records in the kaltura.delivery_profile table so that they point to the LB's addr rather than the node directly.