I don't know if you can access the SSH remotely for that unit I tried to search here on the forum but I couldn't find someone who can remotely access the miner through SSH.
I think the easiest way to remotely access your miner is by using cloud service from awesomeminer.
Another thing is to set up a VPN on raspberry pi you can check this
https://www.pivpn.io/ found it some suggested it here
https://bitcointalk.org/index.php?topic=2105185.0And then set up your phone or laptop(a device that you can bring outside from your farm) I think you can just install OpenVPN and use the same config that you use on raspberry pi to access the same network.