You can't log into SSH as root. You have to log in as a user, then use the 'su' command to get to be root.
You are also running the 2.xx.xx firmware. Usernames and (I think) passwords have to be in ALL UPPERCASE with this firmware.
As to the 2gb problem, it sounds like it's not mounting the 4th partition, and that your "share" is using the wrong partition. With the default install, there is about 2gb left over on your system partition, so if it's not mounting your data partition, then when you connect to public, it'll give you the remaining space of your root partition. Once you get in via SSH, you should be able to figure out why your data partition isn't mounted. Once you mount the data partition, then all should be well.