I have a setup with a computer on my home network to tunnel into when i'm at work/out and about. I left the default port as is but changed the router to open a port in a high number (10000+) and have the translate to 22 on my LAN. I also setup a dyndns on my router just in case my router crashes so I always am able to connect in when the public IP changes. As for rate limiting, I am afraid I do not know about this but setting a long, complex password will suffice. (Mine is 20 alphanumeric with special chars (and easy to remember :s))