What sshd settings would I need to use in order for affa / rsync to work correctly?
In the server-manager of the sourcehost set:
Secure shell access = Allow...
Allow administrative command line access over secure shell = Yes
Allow secure shell access using standard passwords = Yes
Then, on the Affa server, send the public key using 'affa --send-keys sourcehost'
Now you may set on the sourcehost:
Allow secure shell access using standard passwords = No
What router / ports do I need to pass to the server other than 22 ?
Port 22 only.
What are the security implications of this?
I see none, when you keep your Affa server secure.