I'm currently installing CSF (http://www.configserver.com/) for my Ubuntu server and in CSf you're able to specify the ports you want everyone to be able to access, and if your IP is in the allowed list you can still access any port even if it isn't on the port list. I was wondering if it'd be stupid to block the SSH port from everyone and only allow access from the allowed list of IPs. Is it a good idea, or not?
Expanding on what @piotrek wrote: It depends.
If you only need access from the same location, and that location as a static IP that won't change, then you should be okay. But if you ever need access from outside or if you static IP changes, then you would need to go into the server and change it otherwise you could potentially lock yourself out.
SSH is a huge target, but SSH itself is secure. As long as your users use strong password, or you only allow access via ssh-keys. The chances of it becoming hacked are slim.
Block traffic on the DShield Block List and the Spamhaus DROP List
depends on your situation. if ssh is not required to be accesses from all over the world then sure, do it. it costs you nothing and certainly complicates an attacker's life